Andrew M. Frederickson

MRI Findings in Patients with a History of Failed Prior Microvascular Decompression for Hemifacial Spasm: How to Image and Where to Look

BACKGROUND AND PURPOSE: A minority of patients who undergo microvascular decompression for hemifacial spasm do not improve after the first operation. We sought to determine the most common locations of unaddressed neurovascular contact in patients with persistent or recurrent hemifacial spasm despite prior microvascular decompression. MATERIALS AND METHODS: Eighteen patients with a history of a microvascular decompression presented with persistent hemifacial spasm. All patients underwent thin-section steady-state free precession MR imaging. Fourteen patients underwent repeat microvascular decompression at our institution. Images were evaluated for the following: the presence of persistent vascular compression of the facial nerve, type of culprit vessel (artery or vein), name of the culprit artery, segment of the nerve in contact with the vessel, and location of the point of contact relative to the existing surgical pledget. The imaging findings were compared with the operative findings. RESULTS: In 12 of the 18 patients (67%), persistent vascular compression was identified by imaging. In 11 of these 12 patients, the culprit vessel was an artery. Compression of the attached segment (along the ventral surface of the pons) was identified in most patients (58%, 7/12). The point of contact was proximal to the surgical pledget in most patients (83%, 10/12). The imaging interpretation was concordant with the surgical results regarding artery versus vein in 86% of cases and regarding the segment of the nerve contacted in 92%. CONCLUSIONS: In patients with persistent hemifacial spasm despite microvascular decompression, the unaddressed vascular compression is typically proximal to the previously placed pledget, usually along the attached segment of the nerve. Re-imaging with high-resolution T2-weighted MR imaging will usually identify the culprit vessel.

Microvascular decompression for hemifacial spasm in patients >65 years of age: an analysis of outcomes and complications.

Few data are available to quantify the risks and benefits of microvascular decompression (MVD) in elderly patients with hemifacial spasm.

MRI of the Trigeminal Nerve in Patients With Trigeminal Neuralgia Secondary to Vascular Compression.

OBJECTIVE Trigeminal neuralgia is a debilitating facial pain disorder, frequently caused by vascular compression of the trigeminal nerve. Vascular compression that results in trigeminal neuralgia occurs along the cisternal segment of the nerve. CONCLUSION Imaging combined with clinical information is critical to correctly identify patients who are candidates for microvascular decompression. The purpose of this article is to review trigeminal nerve anatomy and to provide strategies for radiologists to recognize important MRI findings in patients with trigeminal neuralgia.

Reduction in high-frequency hearing loss following technical modifications to microvascular decompression for hemifacial spasm

OBJECT Microvascular decompression is a safe and effective procedure to treat hemifacial spasm, but the operation poses some risk to the patients hearing. While severe sensorineural hearing loss across all frequencies occurs at a low rate in experienced hands, a recent study suggests that as many as one-half of patients who undergo this procedure may experience ipsilateral high-frequency hearing loss (HFHL), and as many as one-quarter may experience contralateral HFHL. While it has been suggested that drill-related noise may account for this finding, this study was designed to examine the effect of a number of techniques designed to protect the vestibulocochlear nerve from operative manipulation on the incidence of HFHL. METHODS Pure-tone audiometry was performed both preoperatively and postoperatively on 67 patients who underwent microvascular decompression for hemifacial spasm during the study period. A change of greater than 10 dB at either 4 kHz or 8 kHz was considered to be HFHL. Additionally, the authors analyzed intraoperative brainstem auditory evoked potentials from this patient cohort. RESULTS The incidence of ipsilateral HFHL in this cohort was 7.4%, while the incidence of contralateral HFHL was 4.5%. One patient (1.5%; also included in the HFHL group) experienced an ipsilateral nonserviceable hearing loss. CONCLUSIONS The reduced incidence of HFHL in this study suggests that technical modifications including performing the procedure without the use of fixed retraction may greatly reduce, but not eliminate, the occurrence of HFHL following microvascular decompression for hemifacial spasm.

The utility of calcium phosphate cement in cranioplasty following retromastoid craniectomy for cranial neuralgias

Abstract Background. Following retromastoid craniectomy for microvascular decompression of the fifth or seventh cranial nerve, the preferred method and value of cranioplasty remains disputed. Methods. In this study, we report the functional outcome of calcium phosphate cranioplasty following first-time microvascular decompression in 79 consecutive patients who underwent operations over a one-year period. Results. No patient experienced a deep infection, cerebrospinal fluid leak or undue incisional pain at long-term follow-up. Additionally, all patients stated that they were satisfied with the cosmetic outcome. Discussion. Although this technique is unlikely to affect the rates of infection and postoperative pain, we believe that the low rate of CSF leak provides a unique advantage over other currently used methods of closing retromastoid craniectomies.

Pathogenesis of Trigeminal Neuralgia

Facial pain is a common and nonspecific symptom that is associated with known and unknown etiologies. Because the most effective therapeutic interventions address a disorder’s etiopathogenesis, it is important, when possible, to properly classify patients with different etiologies of facial pain. This is particularly true for trigeminal neuralgia (TN), because of the intensity of the pain associated with this disorder. Historically, the term TN has been used to refer to several different conditions. Taken in its most literal and general form, trigeminal neuralgia denotes pain that occurs within the dermatomal distribution of the trigeminal nerve. Many clinicians, however, reserve the term, TN, to signify a more specific disorder, which manifests as attacks of sudden, unilateral, and lancinating facial pain with characteristic triggers (e.g., light touch, cold air). These attacks may result from vascular compression of the trigeminal nerve near its entry into the brainstem (Jannetta 1967; Gardner and Miklos 1959). Vascular compression as the etiopathogenesis of TN, however, occurs in a minority of patients with facial pain. Furthermore, facial pain that does not fit this description completely may also be associated with probable incidental vascular compression.

Hemifacial spasm caused by an aberrant jugular branch of the ascending pharyngeal artery

Abstract We present the first report of a case of hemifacial spasm caused by an anomalous, enlarged branch of the ascending pharyngeal artery and treated with microvascular decompression. Clinicians must appreciate unusual causes of hemifacial spasm so that patients are not denied a curative operation due to atypical radiographic findings.