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Microneurosurgery

Following microneurosurgery, we generally recommend initiation of neurosensory exercises as soon as the area supplied by the repaired nerve begins to respond to painful stimuli and static light touch (usually within 3 to 6 months after surgery).

From: Current Therapy In Oral and Maxillofacial Surgery , 2012

Dentoalveolar Surgery

Shahrokh C. Bagheri DMD, MD , ... Shahrokh C. Bagheri DMD, MD , in Clinical Review of Oral and Maxillofacial Surgery, 2008

TREATMENT

The two most important factors in successful microneurosurgery are correct patient selection (diagnosis) and prompt evaluation of suspected nerve injuries. Surgical treatment may include nerve exploration with identification of nerve pathology such as a neuroma in continuity, lateral exophytic neuroma, lateral adhesive neuroma, and partial transaction or transaction with a stump neuroma. Specific intraoperative findings will dictate the surgical treatment modality of choice.

Under general nasal endotracheal anesthesia, bupivacaine with epinephrine was injected into the soft tissue of the operative field in addition to an inferior alveolar nerve block for vasoconstriction of the associated proximal vessels. Using 3.5X loop magnification (or an operating microscope) and fiberoptic lighting, incisions were made along the gingival margins of premolar and molar teeth, on both the buccal and lingual aspects of the mandible. The mucoperiosteum was elevated from the region of the bicuspids and posteriorly up the ascending ramus. The periosteum was sharply incised with microscissors, and the lingual nerve was identified and dissected free to reveal a total transaction adjacent to the previously removed third molar with a stump neuroma on the proximal segment. There was a defect in the lingual cortex of the mandible. The distal and proximal nerve stumps were freed of surrounding scar tissue, the proximal amputation neuroma was excised, and the distal nerve stump was freshened to ensure viable fascicles (Figure 5-3, A ). Subsequently, the nerve endings were reanastomosed (neurorrhaphy) in a tension-free manner (tension across the suture line of greater than 25g will significantly compromise regeneration) using 8-0 nylon sutures (Figure 5-3, B ). The anastomosis was guarded by a resorbable flexible collagen nerve cuff to avoid fibrous tissue ingrowth (Figure 5-3C). The mucosal incision was closed with chromic sutures, and the patient was extubated.

Postoperatively the patient was closely monitored for adequate wound healing and subsequent neurosensory reeducation exercises. At 1-year follow-up, the patient demonstrated both subjective and objective signs of left lingual nerve sensory function.

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Complications of Various Treatment Options for Trigeminal Neuralgia

Anil Nanda , Devi Prasad Patra , in Complications in Neurosurgery, 2019

Microvascular Decompression

MVD is one of the safest, albeit invasive, procedures in microneurosurgery. Complications after MVD have been dramatically reduced over the years, with the lowest rates reported in high-volume centers. ³⁸ Specific complications may include cranial nerve dysfunctions during manipulation of the nerves in the cerebellopontine angle. Some degree of hearing loss is not infrequent after MVD; in most cases it is due to conductive impairment secondary to fluid ingression into the middle ear cavity through the mastoid bone. ²⁶ This hearing problem is transient and improves over 2 to 3 weeks. Sensory neural hearing loss is troublesome and should call for more attention. It is the possible result of retraction injury of the cochlear nerve or may be secondary to vasospasm of the anterior inferior cerebellar artery (AICA) during separation of the vessel. Facial nerve paresis, tinnitus, and vertigo are the other few reported cranial nerve complications. ²⁷ Another important complication during surgery is venous bleeding while coagulating the petrosal vein or venous loop over the trigeminal nerve. Though not frequent, the bleeding can sometimes be troublesome and can lead to postoperative cerebellar or brainstem edema. Injury to the transverse or sigmoid sinus during craniotomy and cerebellar contusion during retraction are some important avoidable intraoperative complications. Postoperative complications include cerebrospinal fluid (CSF) leak, wound infection, and CSF rhinorrhea.

Red Flags

•: Percutaneous treatment: indistinct radiologic landmarks, skull base anomalies, abnormal curvature of extracranial internal carotid artery
•: SRS: no specific risk factors; short cisternal segment of trigeminal nerve may pose problem in appropriate fixing of target
•: Microvascular surgery: previous radiosurgery, previous MVD, vascular malformation in the cerebellopontine angle
•: Previous medical therapy (especially prolonged dopamine agonist therapy)
•: Lesions invading the cavernous sinus

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Endoscopic Approaches to Skull Base Lesions, Ventricular Tumors, and Cysts

Nancy McLaughlin , ... Sheri K. Palejwala , in Principles of Neurological Surgery (Third Edition), 2012

Tumor Removal

The dura mater can be opened in a cruciform fashion or in a half circle with the inferior flap reflected caudally. The tumor resection uses the same techniques as those used in microneurosurgery.

For extremely large tumors, an internal debulking using two suctions is preferred because it enables controlled removal of tumor with less trauma to the normal pituitary, stalk, and cavernous sinus contents. Once the posterolateral tumor dissection is complete (from CS to CS laterally and posteriorly toward the clivus-dorsum junction), the superior part of the dura is opened to pursue superolateral dissection. Grasping and pulling should be avoided. Final inspection is undertaken in a clockwise fashion. Residual gland is often found plastered to the undersurface of the diaphragma sella. If the diaphragma does not descend concentrically, residual tumor in the suprasellar space should be suspected and reviewed. If suprasellar dissection is necessary, the tuberculum sellae must be removed.

In cases of circumscribed pituitary adenomas, particularly for the functional ones, an extracapsular dissection is preferred. In these situations, care must be taken not to enter the pituitary pseudocapsule. A plane between the capsule and the normal gland is encountered and followed all around until the tumor is completely disconnected and removed en bloc.

In the advent of cavernous sinus extension, the medial cavernous wall can be explored from within the sella. Because the carotid siphon is usually displaced anterolaterally, the tumor can be followed inside the medial compartment of the CS safely.

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Pineal Gland Disorders and Circadian Rhythm Alterations in Pregnancy and Lactation

Ana-Maria Zagrean , ... Anca Maria Panaitescu , in Maternal-Fetal and Neonatal Endocrinology, 2020

17.1.1.3.1 Surgical Therapeutic Intervention

Surgical treatment is rarely required during pregnancy, but when needed, it is best performed during the second trimester. ⁹ The neurosurgical approach is challenging because the pineal region is deeply located, with important vascular structures situated nearby. However, recent advances in microneurosurgery, anaesthesiology, stereotactic procedures, and neuroendoscopic techniques offer the opportunity to treat lesions in the pineal region with acceptable outcomes during the second trimester. After obtaining a tumor sample, immunocytochemistry can be used for identifying the tumor type, including the use of staining for alpha fetoprotein, beta subunit of hCG, and placental alkaline phosphatase. Gross tumor resection may be postponed according to the histological subtype until after delivery; therefore, biopsy should precede other treatments.

Surgical removal of pineal parenchyma, along with primary pineal tumors or tumors invading the pineal gland (pinealectomy), can cause low serum levels of melatonin and alterations of circadian rhythms, in addition to the already-diminished secretion of melatonin caused by the tumor. ^7a Stereotactic radiosurgery (using a gamma knife or cyberknife) can be used to treat pineal region tumors, either as the primary method or after conventional treatments have been used.

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Vascular Malformations (Arteriovenous Malformations and Dural Arteriovenous Fistulas)

Ghaus M. Malik , Sandeep S. Bhangoo , in Principles of Neurological Surgery (Third Edition), 2012

Grading Systems

Clinicians have been attempting to classify AVMs with the goal of helping patients understand the risks by comparison to historical outcomes. An ideal classification system would have the flexibility to cover many pathological variants, the simplicity to be used in a bedside fashion, and the utility to prognosticate. The variability and rarity of AVMs, however, have made this goal difficult to achieve in practice. Several classification schemes have been proposed. ^10,11 Of these, the Spetzler-Martin system (Table 14.2) ¹² has the most widespread use and should be known by the practicing neurosurgeon. Grades I and II AVM patients generally tolerated resection without morbidity while grade IV and V AVMs had higher risks of postoperative deficits. Retrospective and prospective studies have shown its utility for surgical decision making. ^12,13 There are several weaknesses of this system, however. First, it lacks the ability to assess risks for interventions other than exclusive microneurosurgery. Second, the studies were carried out by a highly experienced vascular team and may not necessarily be applicable to a general neurosurgeon's ability. Third, despite its simplicity, interobserver variability can still occur. ¹⁴ Finally, there is continuing concern that this system may oversimplify many AVMs. A more recent classification scheme attempts to add deep perforator supply and nidus diffuseness parameters to the Spetzler-Martin system ¹⁵ as predictors of higher surgical morbidity rates. The chief drawback is the difficultly applying the diffuseness parameter based on imaging (Fig. 14.4). These factors, however, have been recognized to make microsurgical resection more challenging.

In most of the grading schemes the size measurement is taken as a linear parameter, which when taken in the context of volume, has tremendous variation within the range of dimension. As an example, the spherical volume of a 5.54-cm-diameter AVM is approximately four times greater than an AVM measuring 3.5 cm, even though both of them are assigned 2 points in the Spetzler-Martin scale. Treatment with radiosurgery is volume dependent. In addition, several series have shown that volume is a better predictor of microsurgical risk and outcomes. The approximate volume can be determined by the formula: (length × width × height)/2. These measurements can be obtained from the anteroposterior (AP) and lateral views of the angiogram corrected for magnification.

Future attempts at classification may include more parameters, thus increasing the complexity beyond a simple bedside assessment. The ubiquity of computational devices even at the bedside, however, should allow for greater access to data-mining systems that can generate more granulated prognosis based on an ever greater number of parameters. Future studies, therefore, should focus on making classification schemes accurate rather than simple.

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Meningiomas, Part I

Ali Tayebi Meybodi , ... Arnau Benet , in Handbook of Clinical Neurology, 2020

Arachnoid Reflections

Historical perspective

The arachnoid was unknown prior to three centuries ago. Gerardus Blasius (1626–1692) was the first to describe a third covering layer between the dura and pia mater. Feredrick Ruysch coined the term "arachnoid" in 1692 (Bakay, 1991; Sanan and van Loveren, 1999; Thakur et al., 2012; Adeeb et al., 2013). Ridley and Magendie proved that the arachnoid was a distinct layer between the outer dura and inner pia (Froelich et al., 2008; Thakur et al., 2012). In a landmark study in 1875, Ernst Axel Henrik Key (1832–1901) and Magnus Gustaf Retzius (1842–1919) described a detailed morphology of the subarachnoid cisterns by injecting blue dye to the subarachnoid space (Key and Retzius, 1875). They showed that the subarachnoid space was compartmentalized although it was intercommunicating (Nauta et al., 1983; Bakay, 1991; Di Ieva et al., 2012). Liliequist used pneumoencephalography to describe a barrier membrane in front for the brainstem that prevented the transfer of subarachnoid air to the supratentorial cisterns (Liliequist, 1956, 1959). After all these landmark studies and several others (Engels, 1958; Epstein, 1965; Lewtas and Jefferson, 1966; Lang and Nadjmi, 1973 ), Yaşargil was the first to emphasize the importance of subarachnoid cisterns in microneurosurgery. However, he stressed the contents of the cisterns rather than their walls and membranes ( Yasargil et al., 1976). Several studies thereafter focused on the detailed structure, contents, and attachments of arachnoid membranes to increase the efficacy of microneurosurgical maneuvers and minimize complications (Matsuno et al., 1988; Brasil and Schneider, 1993; Vinas et al., 1996a,b; Buxton et al., 1998; Rhoton, 2000f; Vinas and Panigrahi, 2001; Lü and Zhu, 2003; Lü and Zhu, 2005a; Lü and Zhu, 2005b; Fushimi et al., 2006; Martins et al., 2006; Lü and Zhu, 2007; Froelich et al., 2008; Wang et al., 2008; Inoue et al., 2009).

General considerations

There are two main types of arachnoid membranes: outer and inner. The outer arachnoid membrane surrounds the brain, and it attached externally to the dura such that it prevents escape of the CSF to the subdural space (Gray et al., 2005). The outer membrane is relatively thick, dense, and always intact, except in the areas where the blood vessels, nerves, or the pituitary stalk penetrate (Lü and Zhu, 2005b). The outer membrane is composed of 5–6 layers of cells joined by numerous desmosomes and tight junctions (Gray et al., 2005). Specifically, the outer membrane on the superior wall of the cavernous sinus and optic canals, which covers the tuberculum sellae, ACP, and the PCP, is called the basal arachnoid membrane (BaM).

The subarachnoid space is located between the pia mater and the outer arachnoid membrane. Arachnoid trabeculae traverse the subarachnoid space and become continuous with the pia mater, which is similar in cellular structure with the outer membrane, except that it is composed of one to two layers of cells joined mainly by desmosomes and gap junctions (Gray et al., 2005).

Subarachnoid cisterns can be simply defined as dilated spaces within the subarachnoid space (Fig. 2.4) (Yasargil et al., 1976). Inner arachnoid membranes are named membranes that compartmentalize the subarachnoid space into cisterns. Arachnoid membranous walls of the cisterns may have a sheet-like discrete structure or appear as fine, indistinct, porous, trabeculated spaces with openings of various sizes (Inoue et al., 2009). Anatomical knowledge of the boundaries and contents of these cisterns help the surgeon to navigate safely and efficiently in the deep corridors between the vessels, nerves, brain tissue, and the skull base (Yasargil et al., 1976).

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Pituitary Surgery

Rudolf Fahlbusch , Michael Buchfelder , in The Pituitary (Third Edition), 2011

Evolving Technologies

Just like in other surgical specialities, a variety of novel technical developments were introduced for surgery of the pituitary gland and its tumours. One unequivocal major progress is the use of the endoscope. Endoscope-assisted microsurgery means that an endoscope is used within the classical microsurgical operation, when the surgeon feels that the additional assets of the endoscope could be helpful. The visual field is no more restricted by the straight beam of light within the nasal tunnel maintained open by the speculum. Introduction of an endoscope into the sphenoid sinus allows a more panoramic visualization of the anatomy, an excellent orientation, and additional control of the radicality of tumor resection. The visual field of the surgeon is thus considerably extended [26]. Alternatively, fully endoscopic procedures no longer require septal dissections and the use of a speculum [99]. A direct perinasal route is chosen and a sphenoidotomy performed. Rather than an operating microscope a monitor is used. To date, few data are available on the hormonal and imaging outcomes which allow a comparison of remission and complication rates, respectively, of open microsurgical procedures and entirely endoscopic operations [100]. One disadvantage of the endoscopic technique is the learning curve with a technically somewhat different procedure during which the surgeon controls his instruments from a screen rather than from the lenses of the operating microscope. Thus, the operating time is frequently extended. The three-dimensional view, which the operating microscope allows, is lost and the color information is inferior to that obtained with sophisticated microscopic equipment. With "extended" nasal approaches, lesions become accessible transsphenoidally which have previously been considered contraindications for nasal approaches [102]. However, to date still most of the data available on safety and efficacy of pituitary operations come from microsurgical operations.

Neuronavigation is to date widely used in the entire field of microneurosurgery and may be used during pituitary operations. The three-dimensional data set provided by preoperative imaging is related to the patient's head in the operation room. Critical structures such as the tumor shape or the brain-supplying major arteries can be localized with a "pointer" or segmented and superimposed onto the surgical field [26,103]. Thus, additional anatomical orientation is gained. Image-guided surgery can be used in each and every case, but is associated with increased costs and might not be always needed. It is certainly particularly helpful in anatomical variants and reoperations. Neuronavigation to date is highly reliable and substitutes for the traditional fluoroscopic control [104].

The microdoppler system, which is widely used in neurovascular microsurgery, can also be considered a useful technical tool for pituitary operations. It allows localization of the carotid artery within the cavernous sinus or within parasellar tumor. Thus, the likelihood of an arterial lesion is further minimized [105].

Intraoperative magnetic resonance imaging is receiving increasing recognition. Dedicated MR scanners were developed for intraoperative imaging and diagnostic scanners systems were modified for intraoperative use in pituitary surgery [106,107]. While in an ideal case of an intra- and suprasellar adenoma, the elevated arachnoid descends into the sella in only one smooth arachnoidal plane, a complex situation may occur in which residual tumor cannot be directly visualized. There might be tumor hidden below any one of the arachnoidal pouches or in the lateral, anterior, or posterior portions of the sella. Both low- and high-field MR systems are able to detect such residual tumor intraoperatively and thus allow improvement of the radicality of tumor excision, particularly in large tumors [107,108]. Only high-field systems can also depict the parasellar structures with sufficient image quality and thus allow a decision about total removal of intra- and parasellar lesions. In a modern high-field system intraoperative images can be obtained that correspond perfectly to the delayed postoperative scans which constitute the standard of postoperative imaging [108,109]. The relatively high costs of the devices and the necessity of at least partially rebuilding the operating room to make it suitable for the MR are clearly disadvantages of this technology. In several reports, it has been convincingly demonstrated, that even in experienced hands, the rate of total tumor resections could be increased by about one-third [109]. However, even with all the technical refinements in the surgery of pituitary adenomas, the factors defined by the tumor growth characteristics and location and the individual experience and technical skills of the surgeon are still the main determinants of the surgical outcome for an individual patient. Centers with a high case load and experienced neurosurgeons have less complications and achieve a more efficient outcome in terms of both the extent of tumor resection as visualized by imaging and normalization of hormonal oversecretion [110,111].

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Complications of Face and Neck Lift: Recognition, Treatment and Prevention

Joe NiamtuIII DMD , in The Art and Science of Facelift Surgery, 2019

Neurologic Complications

Motor Nerve Injury

The most feared complications of facelift surgery are motor and sensory nerve damage and flap necrosis. These, unlike many of the complications discussed previously, can be tragic for the patient and surgeon as well, leading to damage of reputation and litigation.

Frontal, buccal, zygomatic, marginal mandibular, and cervical nerve injury can result from many different things, including direct injury (clamps, needles, scalpels, and scissors), neuropraxia (stretching from over aggressive retraction), thermal injury from cautery, or compression injury from sutures, edema, hematoma, and other causes. This is very disconcerting for the patient and surgeon in the early postoperative period, but most of these will spontaneously resolve within weeks or months. The gradual return of function to the affected area is seen and greeted with relief by all involved. Patients should be reassured that the nerve weakness is likely temporary but advised (hopefully preoperatively) that return of full function cannot be guaranteed. In the 1200 facelifts I have performed over the past 20 years, I have experienced no permanent motor nerve injuries. Between 8 and 10 patients had unilateral paresis of the buccal, zygomatic, or marginal mandibular branches, with altered animation that returned within 90 to 120 days (Figs. 9.39–9.42 ). Motor nerve injuries that do not seem to improve or those that are severe and include multiple nerve branches should be evaluated after 90 days by a surgeon experienced in microneurosurgery. The buccal and zygomatic branches have numerous anastomoses. For this reason, a permanent injury from a distal injury is rare, but this also makes it difficult to characterize the exact nerve injury. Rami of the zygomatic branch of the facial nerve innervate the lower portion of the orbicularis oculi and, if injured, can affect lid closure. This is an unusual injury, and an affected patient is shown in Fig. 9.39.

The marginal mandibular branch is a commonly affected motor nerve in facelift surgery and can be damaged during dissection, submental liposuction, and chin implant surgery. When a patient with damage to this nerve smiles or rolls their lower lip down, the affected side does not depress, owing to the loss of innervation of the depressor anguli oris and/or the depressor labii (see Figs. 9.40 and 9.41). Sometimes this can also be related to a cervical nerve injury in that the platysma also depresses the lip or corner of the mouth in many patients. In these patients, the motor function of the platysma would likely be involved. When the lip is affected from a marginal mandibular nerve injury, the normal side can be treated with a small amount of neurotoxin to even out the asymmetry (see Fig. 9.41).

Most patients are content to wait for the nerve function to improve. Showing them progress pictures over several months can confirm their improvement and relax nervous patients. Also showing them pictures of other patients with similar injury and resolution reinforces their patience to "wait it out". Anecdotally, this would appear to be one of the most common nerve injuries because I frequently receive calls for advice from novice surgeons who have experienced marginal mandibular paresis and the vast majority have happy endings.

Total main facial nerve trunk injury is rare in facelift surgery because it is protected by the parotid gland but has been documented in rare cases. Injury to the frontal branch is rarer, and I have not experienced this in over 1200 facelifts.

The facial nerve branches are rarely in jeopardy until exiting the parotid gland and crossing the masseter. Novice surgeons should stay over the gland in the safe zone (Fig. 9.43).

An even rarer motor nerve injury that has been documented with facelift surgery is damage to the cranial nerve 11, the spinal accessory nerve. This nerve innervates the sternocleidomastoid (SCM) and trapezius muscles, which assist in turning the head and shrugging the shoulders. The spinal accessory nerve exits on the posterior border of the SCM muscle at Erb's point (the same level of the greater auricular nerve [GAN]) and enters the posterior triangle (Fig. 9.44).

Technically, Erb's point was classically described as a point where the cervical plexus exits from behind the posterior border of the SCM muscle. The four cutaneous nerves of the cervical plexus are the lesser occipital nerve, great auricular nerve, transverse cervical nerve, and supraclavicular nerve. The scientific literature has many different descriptions of "Erb's point" and many articles describe the spinal accessory and GAN emerging from Erb's point. This description will be used in this text.

At this point the platysma ends; the nerve is only protected by skin and variable amounts of subcutaneous fat and fascia and is vulnerable. Although injury is rare, all surgeons should keep in mind that an errant liposuction cannula, aggressive retraction, or lateral thermal damage from cauterization could injure this nerve (Figs. 9.45–9.47).

Figs. 9.45 and 9.46 shows a patient with a spinal accessory nerve injury. The patient healed uneventfully from her facelift, and at her 3-month visit she complained of shoulder pain. Examination showed decreased range of motion and inability to abduct the affected side and confirmed by electromyography. Although the deficit and pain were slowly improving, a microneurosurgeon advised exploration and repair. Although waiting for increased function was an option, postponing the surgery could have closed the window of time for optimal treatment and nerve recovery; therefore the decision was made to explore and repair. Exploration showed a neuroma which was removed, primary nerve repair performed, and the patient regained normal function (see Fig. 9.45). Fig. 9.47 shows an outline of the incision used to treat the neuroma at the level of the injury. This location should be committed to memory because this is in approximation where the nerve is in jeopardy.

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Volume 1

Anitha Nimmagadda , ... Bernard R. Bendok , in Schmidek and Sweet Operative Neurosurgical Techniques (Sixth Edition), 2012

Classification of Spinal Vascular Malformations

The classification of spinal vascular malformations has evolved significantly over the last 150 years as the understanding of the complex pathophysiology of these lesions has continued to improve. The initial classification schemes that were proposed failed to properly categorize the lesions based on their anatomy. The first classification scheme for spinal vascular lesions was proposed by Virchow in 1858. ⁴ Virchow subdivided vascular lesions into two types: angioma cavernosum (lesion without parenchyma between the blood vessels) and angioma racemosum (hamartoma: lesion with parenchyma between the blood vessels). Elsberg, in 1916, was the next to propose a classification scheme for spinal vascular lesions in which he divided them into three categories: aneurysm of spinal vessels, angioma in which a mass of dilated veins penetrates the spinal cord, and dilation of posterior spinal veins. In 1928, Cushing and Bailey proposed yet another classification system in which they divided spinal vascular lesions into two major groups: hemangioblastomas and vascular malformations. The broad group of vascular malformations included plexus of dilated veins, aneurismal varix, venous angioma, and telangiectasias.

Advances in neurointerventional surgery and microneurosurgery during the 1960s and 1970s combined with a clearer understanding of the true pathophysiology of spinal vascular lesions led to the development of a new classification system that divided spinal vascular malformations into types I to IV. This system, which is still widely used today, did not include neoplastic lesions ( Table 91-1). The classification system proposed by Rodesch and colleagues divided spinal vascular malformations into three groups: AVMs, fistulas, and genetic classification of spinal cord arteriovenous shunts. ⁵ The last group was further subdivided into three groups: genetic hereditary lesions (macrofistulas and hereditary hemorrhagic telangectasia), genetic nonhereditary lesions (multiple lesions with metameric or myelomeric associations), and single lesions (incomplete associations of either of the first two categories). The classification system for spinal vascular lesions proposed by Spetzler and colleagues also subdivided the lesions into four large groups: neoplasms, spinal aneurysms, spinal AVMs, and spinal fistulas. ⁶ Arteriovenous fistulas (AVFs) were further subdivided into extradural and intradural (dorsal or ventral). AVMs were further classified into extradural-intradural or intradural. Intradural AVMs were further subclassified as intramedullary, compact, diffuse, and conus medullaris. This separate classification of conus medullaris AVMs is unique to the Spetzler system. ⁶

Of these classification systems, the type I through IV system remains the most commonly used. Type 1 spinal vascular malformations are actually dorsal intradural AVFs with the fistulas located in the proximal dura of the nerve root sleeve. These malformations are the most common spinal vascular malformation. They are subdivided into type A, in which the malformation is supplied by a single arterial feeder, and type B, in which the malformation is supplied by multiple arterial feeders. ⁷ They occur most commonly in the lower thoracic and upper lumbar segments of the spinal cord, T4–L3, with the peak incidence between T7 and T12. ⁸

In type IA malformations, the fistula is formed by an anastomosis of a dural branch of a radicular artery (very rarely a radiculomedullary artery) and a radiculomedullary vein.

In type IB malformations, there are anastomoses between branches of several adjacent radicular arteries and a radiculomedullary vein. The radiculomedullary vein becomes arterialized owing to increased flow and pressure, which it transmits to the valveless coronal plexus and the longitudinal veins. The radiculomedullary vein becomes enlarged and tortuous, leading to its classic angiographic appearance. Studies have shown that the mean intraluminal venous pressure is increased to 74% of the systemic arterial pressure. ⁹ The normal pressure in the coronal venous plexus is approximately twice that of the epidural venous plexus. This significant pressure gradient is necessary for normal venous drainage. When it is compromised, as in the case of type I spinal AVMs, venous hypertension develops. Venous hypertension then leads to the development of progressive myelopathy due to transmission of increased venous pressure to the spinal cord parenchyma, resulting in multiple pathologic changes including demyelination.

Type II spinal vascular malformations are true AVMs of the spinal cord with multiple arterial feeders, a nidus, and draining vein(s). They are structurally similar to cerebral AVMs. They are the second most common spinal vascular malformation. They are high-flow, low-resistance, high-pressure lesions. ⁶ The arterial feeders are usually branches of the anterior spinal artery or the posterior spinal arteries.

Type III spinal vascular malformations, also known as juvenile AVMs or metameric AVMs, are more diffuse lesions that can encircle the entire spinal cord. Involvement of all the derivatives of a metamere in the AVM (skin, bone, muscle, dura, nerve roots, and spinal cord) has been described as Cobb's syndrome.

Spinal artery aneurysms or venous aneurysms are found in 20% to 40% of patients with intramedullary AVMs. The presence of a spinal artery aneurysm has been associated with an increased risk of hemorrhage. ¹⁰

Type IV spinal vascular malformations are actually perimedullary AVFs and were first described by Djindjian and colleagues. The fistula occurs ventrally and in the midline between the anterior spinal artery and the coronal venous plexus. ¹¹ In contrast to type I dural AVFs, type IV lesions are high-flow fistulas. These lesions are further classified into three subtypes. Type A (Merland subtype I) is a solitary AVF fed by the anterior spinal artery (ASA) and located at the conus medullaris or the filum terminale. There is moderate venous hypertension without enlargement of the ASA. The ascending draining vein is only minimally dilated. Type B (Merland subtype II) is a small group of AVFs located at the conus and supplied by the anterior and posterior spinal arteries. The feeding arteries and draining veins are moderately dilated. Venous ectasia is present at the site of the fistula, and the ascending perimedullary veins are tortuous and enlarged. Type C (Merland subtype III) is a single large AVF supplied by the anterior and posterior spinal arteries and located in the cervical or thoracic spinal cord. ¹² The draining vein is significantly dilated and ectatic and may be embedded within the spinal cord.

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Cervicofacial Rhytidectomy

In Cosmetic Facial Surgery, 2011

Neurologic Complications

Motor Nerve Injury

Two of the most feared complications of facelift surgery are motor and sensory nerve damage and flap necrosis. ^31-33 These, unlike many of the complications discussed previously, can be tragic for the patient and surgeon as well, leading to damage of reputation and litigation.

Frontal, buccal, zygomatic, marginal mandibular, and cervical nerve injury can result from many different things, including direct injury (clamps, needles, scalpels an scissors), neuropraxia (stretching from over aggressive retraction), thermal injury from cautery, or compression injury from sutures, edema, hematoma, and other causes. This is very disconcerting for the patient and surgeon in the early postoperative period, but most of these will spontaneously resolve within weeks or months. The gradual return of function to the affected area is seen and greeted with relief by all involved. Patients should be reassured that the nerve weakness is likely temporary but advised (hopefully preoperatively) that return of full function cannot be guaranteed. In the hundreds of facelifts I have performed over the past 12 years, I have experienced no permanent motor nerve injuries. Four or five patients had unilateral paresis of the buccal, zygomatic, or marginal mandibular branches, with altered animation that returned within 90 to 120 days (Figures 9-199 and 9-200 ). Motor nerve injuries that do not seem to improve or those that are severe and include multiple nerve branches should be evaluated by a surgeon experienced in microneurosurgery after 90 days. The buccal and zygomatic branches are very arborized and intertwined. For this reason, a permanent injury is rare, but this also makes it difficult to characterize the exact nerve injury.

Rami of the zygomatic branch of the facial nerve innervate the lower portion of the orbicularis oculi and if injured can affect lid closure. This is an unusual injury, and an affected patient is shown in Figure 9-201.

The marginal mandibular branch is a commonly affected motor nerve and can be damaged during cervicofacial rhytidectomy, submental liposuction, and chin implant surgery. When a patient with damage to this nerve smiles, the affected side does not depress, owing to the loss of innervation of the depressor anguli oris and/or the depressor labii. Sometimes this can also be related to a cervical nerve injury in that the platysma also depresses the lip or corner of the mouth in many patients. In these patients, the motor function of the platysma would likely be involved. Figure 9-202 shows a patient with a right-sided marginal mandibular nerve injury. To temporarily minimize this asymmetry, the normal side can be treated with a small amount of neurotoxin to even out the asymmetry. Most patients are content to wait for the nerve function to improve.

The frontal branch of the temporal nerve can be disrupted during brow lift procedures or in the area of the zygomatic arch during facelift procedures. In over 500 facelifts, I have never personally experienced a frontal branch injury. If it does occur, the unaffected side can be treated with neurotoxin to temporarily control asymmetric movement.

Sensory Nerve Complications

Facelift patients must be educated in the fact that they will all have some component of sensory deficit, especially in the pre- and postauricular regions. Generally this will spontaneously resolve over a 90-day period. They must be reassured when it takes longer; reinnervation usually ensues with time. Regardless of the amount of preoperative discussion about temporary paresthesia, extended numbness can cause patient anxiety in the postoperative period. I tell all preoperative facelift patients that the area in front of, below, and behind the ear are likely to be numb for up to 90 days. Some patients experience very little paresthesia or improve in the first several weeks, but most patients will be numb for a while. This can work to positive advantage because uncomplicated facelift surgery is generally not extremely painful, in part due to the paresthesia.

The infraorbital and mental sensory nerves are at risk during facial implant procedures, which are frequently performed with facelift surgery.

Perhaps the most commonly affected sensory nerve is the greater auricular nerve (GAN). This nerve crosses the sternocleidomastoid (SCM) muscle approximately 6.5 cm below the external auditory canal (see Figure 9-7). As mentioned numerous times in the previous sections of this chapter, there is very little subcutaneous tissue in the mastoid region and the upper regions of the SCM muscle. In this region, the dermis is virtually intimate to the fascia of the SCM, and it is not uncommon to expose muscle fibers when performing flap dissection in this area. It is also possible to damage the GAN as it superficially crosses the SCM (Figure 9-203). Figures 9-7, 9-9, and 9-59 show these relationships. This nerve often has branches, and I have inadvertently, although never intentionally, severed these, resulting in no permanent sensory deficit. Figure 9-204, A shows a transected GAN. If the nerve is transected, it should be anastomosed with 7-0 Prolene suture (see Figure 9-204, B ). If for any reason it cannot be repaired, the stumps should be tagged with a permanent suture for later identification if necessary.

A damaged or repaired GAN can also develop a neuroma, which manifests as an induration palpable through the skin over the area of the nerve. A GAN neuroma can be painful and when pressed by the examiner can radiate pain into the nerve distribution.

The transverse cervical nerve horizontally crosses the SCM inferior to the greater auricular nerve and provides sensory innervation to the skin over the anterior triangle of the neck. This nerve can be damaged in a low inferior cervical dissection.

Although a very rare injury, injury to the spinal accessory nerve (cranial nerve XI, motor nerve) has occurred in facelift surgery. This nerve exits on the posterior of the SCM (Erb's point). Since this nerve is posterior and deep, it remains out of the field of dissection of most facelift flaps, but the surgeon must keep its presence in mind because the physical problems of shoulder droop are very problematic. Figure 9-205 shows the relation of vulnerable nerves during cervical dissection.

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