Cutaneous-evoked tinnitus. II. Review Of neuroanatomical, physiological and functional imaging studies.

Cutaneous-evoked tinnitus is a clinical entity that has not been reported previously in the neurootological literature. Herein, a neuroscience framework that encompasses several distinct areas of research is used to conceptualize and help understand this phenomenon. We review normal neuroanatomical and physiological interactions between auditory and somatosensory systems in mammals. Also considered are mechanistic accounts of lesion-induced changes in the CNS following deafferentation/deefferentation of peripheral sensory or motor structures that may have a relationship to this phenomenon, as well as the role of functional imaging modalities in studying various phantom perceptions.

Cutaneous-evoked tinnitus. I. Phenomenology, psychophysics and functional imaging.

DC00166e and acute unilateral deafferentation of the auditory periphery (auditory and vestibular afferents) can induce changes in the central nervous system that may result in unique forms of tinnitus. These tinnitus perceptions can be controlled (turned on and off) or modulated (changed in pitch or loudness) by performing certain overt behaviors in other sensory/motor systems. Clinical reports from our laboratory and several other independent sources indicate that static change in eye gaze, from a neutral head-referenced position, is one such behavior that can evoke, modulate and/or suppress these phantom auditory events. This report deals with a new clinical entity and a form of tinnitus that can be evoked directly by cutaneous stimulation of the upper hand and fingertip regions. In 2 adults, cutaneous-evoked tinnitus was reported following neurosurgery for space-occupying lesions at the base of the skull and posterior craniofossa, where hearing and vestibular functions were lost completely and acutely in one ear (unilateral deafferentation) and facial nerve paralysis (unilateral deefferentation) was present either immediately following neurosurgery or had occurred as a delayed-onset event. Herein, we focus on the phenomenology of this discovery, provide perceptual correlates using contemporary psychophysical methods and document in one individual cutaneous-evoked tinnitus-related neural activity using functional magnetic resonance imaging. In a companion paper, neuroanatomical and physiological interactions between auditory and somatosensory systems, possible mechanistic accounts and relevant functional neuroimaging studies are reviewed.

Intraoperative loss of auditory function relieved by microvascular decompression of the cochlear nerve.

BACKGROUND: Brainstem auditory evoked potentials (BAEP) are useful indicators of auditory function during posterior fossa surgery. Several potential mechanisms of injury may affect the cochlear nerve, and complete loss of BAEP is often associated with postoperative hearing loss. We report two cases of intraoperative auditory loss related to vascular compression upon the cochlear nerve. METHODS: Intra-operative BAEP were monitored in a consecutive series of over 300 microvascular decompressions (MVD) performed in a recent twelve-month period. In two patients undergoing treatment for trigeminal neuralgia, BAEP waveforms suddenly disappeared completely during closure of the dura. RESULTS: The cerebello-pontine angle was immediately re-explored and there was no evidence of hemorrhage or cerebellar swelling. The cochlear nerve and brainstem were inspected, and prominent vascular compression was identified in both patients. A cochlear nerve MVD resulted in immediate restoration of BAEP, and both patients recovered without hearing loss. CONCLUSION: These cases illustrate that vascular compression upon the cochlear nerve may disrupt function, and is reversible with MVD. Awareness of this event and recognition of BAEP changes alert the neurosurgeon to a potential reversible cause of hearing loss during posterior fossa surgery.

Functional outcome and the effect of cranioplasty after retromastoid craniectomy for microvascular decompression.

BACKGROUND: While the efficacy of retromastoid craniectomy for microvascular decompression for hyperactive cranial nerve syndromes is well established, there is no real information regarding the functional outcome of these operations. The purpose of this retrospective questionnaire study is to assess functional outcome regarding presence and duration of postoperative headache, incisional pain, and the time to return to normal activity in patients undergoing retromastoid craniectomy for microvascular decompression. The effect of closure with bone chips or cranioplasty in the defect upon these functional outcomes was studied, as was the influence of the particular nerve that was the object of decompression. METHODS: Four-hundred and ninety-five consecutive patients were contacted and 320 (65%) returned questionnaires with enough information to be suitable for analysis. RESULTS: The incidence of postoperative headache was initially 60.1%, dropping to 28.8% at 1 month and 16.8% at 6 months. Incisional pain likewise declined with time, noted in 25.8% at 1 month and only 13.1% at 6 months. Use of a cranioplasty made no significant difference in influencing either postoperative headache or incisional pain, nor was the nature of the procedure a significant factor. CONCLUSION: Twenty-five percent of patients resumed normal activity by 3 weeks, 50% by 1 month, and 90% by 3 months. Overall, 98% of patients responding reported returning to normal activity. Therefore, although there is an incidence of postoperative headache and incisional pain, these decrease with time and do not seem to interfere with the return to normal activity, nor are they affected by placement of a cranioplasty or the nature of the operation.

Delayed facial weakness after microvascular decompression of cranial nerve VII.

BACKGROUND: Retromastoid craniectomy and microvascular decompression of cranial nerve VII for hemifacial spasm is a well accepted and effective treatment. Risks of the operation relate to the surgical approach in general and to the seventh nerve in particular. Delayed facial weakness is an unusual and little-described complication of the procedure. The purpose of this review is to describe this complication and the characteristics of the patients so affected. METHODS: Between 1972 and 1996, 985 patients have undergone microvascular decompression for hemifacial spasm. During this time, 28 patients (2.8%) undergoing decompression of the facial nerve and 1 patient undergoing decompression of the cochlear nerve for tinnitus developed delayed facial palsy. RESULTS: The weakness was at least a House Grade III or worse and was complete in 11 of the patients. The time to occurrence averaged 12 days, with a tight range of 7 to 16 days. There were no factors such as duration of symptoms, intraoperative findings, or preoperative botulinum injections that were predictive of this postoperative weakness. In all patients there was almost complete recovery (House Grade I or II). CONCLUSIONS: Delayed facial weakness after MVD of CN VII can occur in up to 3% of cases. The onset of weakness after operation is consistent in its timing, occurring on average 12 days after the procedure. Although the etiology of this complication is uncertain, the palsy spontaneously resolves with a good or excellent outcome.

Comparison of tension band wiring and lateral mass plating for subaxial posterior cervical fusion.

BACKGROUND: Two instrumentation methods for subaxial posterior cervical fusion are compared in terms of efficacy, morbidity, and significant cost-related variables. METHOD: Thirty-four patients with tension band wiring and 14 patients with lateral mass plating are retrospectively compared in a single surgeon's experience between 1989 and early 1995. RESULTS: Both groups were similar in regard to operative indication (about 40% trauma, 30% degenerative changes in each group), postoperative immobilization (hard collar only used in 82% of patients wired and 79% of patients plated), and number of levels fused (mean, 1.7 in each group). Mean follow-up is 23 months for wiring and 35 months for plating. Pseudoarthrodesis occurred in one patient undergoing wiring and in none of the patients plated. Both methods resulted in complications (7 in 34 cases of wiring, 4 in 14 cases of plating), but no patient experienced neurologic decline. Statistically significant differences between the two groups were found for estimated blood loss, operating room time, and hardware cost, but not for postoperative orthosis or length of stay. CONCLUSION: In some instances when subaxial posterior fusion is performed, tension band wiring may be more cost-efficient. Tension band wiring and lateral mass plating seem to have comparable efficacy and morbidity, but the indications for each technique differ.

The surgical management of chronic cluster headache.

OBJECTIVE: Chronic cluster headache occurs in less than 10% of cluster headache sufferers, but remains an intractable medical problem. Surgical treatments have also been limited in their effectiveness. The authors describe their experience with attempted surgical amelioration of chronic cluster headache. DESIGN: Twenty-eight patients, including two with bilateral cluster headache, underwent 39 operations for microvascular decompression of the trigeminal nerve, alone or in combination with section and/or microvascular decompression of the nervus intermedius. Follow-up averaged 5.3 years. RESULTS: Initial postoperative success described as 50% relief or greater was achieved in 22 (73.3%) of 30 first-time procedures and greater than 90% relief in half (15 of 30) of these. Long-term follow-up saw this success rate (excellent or good) drop to 46.6%. Repeat procedures have little success, with 7 of 8 failing at long-term follow-up. Morbidity and neurological deficit from the operations was minimal. CONCLUSIONS: Chronic cluster headache remains a debilitating and poorly controlled syndrome. Although various surgical treatments have had limited success, microvascular decompression of the trigeminal nerve with section of the nervus intermedius compares very favorably to other destructive techniques without the accompanying neurologic deficits. It is, therefore, our recommendation as the first-line operative treatment of chronic cluster headache.

Surgical management of geniculate neuralgia.

BACKGROUND: Geniculate ganglion or nervus intermedius neuraigia is an unusual condition resulting in deep ear pain with or without signs of atypical trigeminal neuralgia, deep face, or throat pain. This article describes an experience with 14 patients who came to the neurosurgical service at the University of Pittsburgh Medical Center with a diagnosis of geniculate neuralgia. METHODS: After failing conservative treatment and after undergoing neurologic, otologic, and dental evaluations, these 14 patients underwent 20 intracranial procedures consisting of retromastoid craniectomies with microvascular decompression of cranial nerves V, IX, and X with section of the nervus intermedius in most cases. RESULTS: At operation, vascular compression of the nerves and nervus intermedius was found, which implicated vascular compression as an etiology of this disorder. Initially, 10 of 14 patients had an excellent outcome (71.5%), 3 experienced partial relief (21.5%), and there was 1 failure (7%). Ten patients were available for long-term (> 12 months) follow-up. Of these 10, 3 retained the excellent result (30%), 6 experienced partial relief (60%), and there was 1 failure (10%). Complications included one transient facial paresis, one facial numbness, one paresis of cranial nerves IX and X, one chemical meningitis, two cerebrospinal fluid leaks, and one superficial wound infection. Of those that fell from the excellent to partial category, this usually involved a return of atypical facial pain, but otalgia remained resolved. CONCLUSIONS: Overall, good results (with excellent or partial relief) were found long term for 90% of patients in this series. The authors recommend microvascular decompression of cranial nerves V, IX, and X with nervus intermedius section for the treatment of geniculate neuralgia.

Microvascular decompression for trigeminal neuralgia. Surgical technique and long-term results.

In summary, it can be concluded that MVD has a long-term success rate equal or superior to percutaneous procedures without the higher rate of permanent neurologic sequelae. It is a safe operation with an almost negligible mortality and low morbidity in skilled hands. If the goal in the treatment of TGN remains obtaining a pain-free state without the need for medication and no permanent neurologic deficit, then MVD remains the definitive procedure of choice for typical TGN.

The value of provocative facet blocking as a predictor of success in lumbar spine fusion.

Studies attempting to correlate facet blocking with successful relief of pain after fusion have reached unfavorable results. These studies, however, did so in a retrospective fashion, and facet blocking was not the sole criterion by which surgical candidates were chosen. The current study is the first to use facet blocking in a prospective fashion and as the definitive criterion by which patients were chosen. Ninety-one patients with chronic low back pain who responded to bracing underwent 197 facet blocks. Twenty-eight patients who had > 70% relief of their pain for >6 h on three separate occasions were surgical candidates and underwent fusion along with two others with mechanical abnormalities but negative blocks. Pre- and postoperative Prolo (Prolo DJ, Oklund SA, Butcher M: Toward uniformity in evaluating results of lumbar spine operations. A paradigm applied to posterior lumbar interbody fusions. Spine 11:601-606, 1986) outcome scores were assigned and the patients underwent self-assessment. Twenty-three of 30 patients had successful fusion. Nineteen of 23 described 90% relief, 3 patients had 50-90% partial relief, and 1 failed by self-assessment. A preoperative mean Prolo score of 3.95 (range 2-7) improved to 7.7 (range 3-10) with fusion. Provocative facet blocking can be used to successfully predict outcome in patients undergoing arthrodesis for chronic low back pain.

Degenerative cervical spondylolisthesis: diagnosis and management in five cases.

Five cases of degenerative subaxial spondylolisthesis of osteoarthritic etiology associated with significant cervical spondylotic myelopathy are described with treatment recommendations. Diagnostic studies included cervical plain films with flexion/extension, magnetic resonance imaging, and computed tomography/myelography. All patients had at least 2 mm of spondylolisthesis at one or more levels, and two patients had movement evident on flexion/extension films. Posterior laminectomy with AME (American Medical Electronics, Richardson, TX, U.S.A.) lateral mass plate and bone fusion was successfully performed in all five patients, three of whom improved one grade on the Nurick classification, whereas the rest improved within the same grade.

Intraoperative mapping of the trigeminal nerve root: technique and application in the surgical management of facial pain.

A method for intraoperative topographic mapping of the trigeminal nerve root using electrophysiological methods is described. A series of 15 patients under general anesthesia during microvascular decompression and selective posterior fossa trigeminal rhizotomy was studied. This method was used to study the localization of fibers of individual subdivisions of the intradural portion of the trigeminal nerve and as a guide for performing physiologically controlled, selective, microsurgical trigeminal rhizotomy.

Rosai-Dorfman disease presenting with multiple orbital and intracranial masses.

Rosai-Dorfman disease is an idiopathic histocytic proliferative disorder typically characterized by painless cervical adenopathy, fever, and weight loss. Extranodal manifestations are responsible for presentation in approximately 25% of patients. Orbital involvement has been described in about 10% of patients. There have been only 16 reported cases of Rosai-Dorfman disease presenting with an intracranial mass. We report an unusual case of a patient presenting with bilateral orbital tumors as well as multiple intracranial masses. Clinical, magnetic resonance imaging, and histopathological features are discussed.

Posterior cervical spine fusion with tension-band wiring.

In this study the authors detail their experience with posterior tension-band wiring for stabilization of the subaxial cervical spine. Fifty-five patients underwent fusion for trauma (41 patients), degenerative disease (13 patients), and tumor (one patient). The fusion rate was 96% (50 of 52 patients) and postoperative immobilization was accomplished by means of a Philadelphia collar in the majority of cases. Tension-band wiring provides a stable construct that is simple to perform, requires fusion of a minium number of motion segments, and allows early mobilization with only a hard collar needed for support. The details of the technique, which has been modified from preliminary descriptions, are discussed.

Factors influencing hearing preservation in acoustic tumor surgery.

In patients who underwent neurosurgery for excision of acoustic tumors, we used correlation and multivariate logistic regression analysis to study relationships among nine variables thought to have value in predicting hearing preservation. These variables included auditory perceptual, auditory neurophysiologic, and imaging-related characteristics of acoustic tumor dimensions. The univariate correlations showed two general trends. The first trend demonstrated relationships among imaging-related acoustic tumor dimensions (size or porus acousticus widening) with either postoperative hearing or brainstem auditory evoked potential (BAEP) abnormalities (tumor size and postoperative hearing; porus acousticus widening and postoperative hearing; tumor size and preoperative BAEP abnormalities). The second trend reflected interrelationships among preoperative audiometric variables that were not related to postoperative hearing outcome. Logistic regression analysis of eight independent variables on the presence or absence of postoperative hearing found that porus acousticus widening was the best prognostic indicator for hearing outcome. When the porus acousticus was widened, the odds ratio was 11:1 that hearing would be lost postoperatively. Viewed as a whole, the literature on prognostic variables related to hearing preservation has been limited, almost entirely, to univariate relationships. To determine more accurately which preoperative variables have unique prognostic value, more complex multivariate, analysis procedures will be required. Additionally, standardized criteria for assessment and reporting of auditory test results are also needed.

Anomalous cross-modal plasticity following posterior fossa surgery: some speculations on gaze-evoked tinnitus.

A unique and intriguing form of subjective tinnitus evoked by eye gaze is reviewed. A new perspective is presented because this condition is sufficiently different from other forms of subjective tinnitus and its manifestation cannot be adequately explained by existing models or conceptual frameworks. Our examination of this topic considers pathophysiologic changes in the central nervous system in the context of deafferentation-induced plasticity. Potential neuroanatomical areas contributing to this effect include a number of distributed and functionally diverse areas in the brainstem and neocortex involved in the auditory control of eye movements. We also consider contemporary psychophysical methods to evaluate the perceptual correlates of this phenomenon and tools for the development of objective tinnitus measurements. Although theoretical and speculative in nature, this article is intended to stimulate interest in, advance knowledge of, and provide a better understanding about this condition.

Auditory perceptual and visual-spatial characteristics of gaze-evoked tinnitus.

Auditory perceptual and visual-spatial characteristics of subjective tinnitus evoked by eye gaze were studied in two adult human subjects. This uncommon form of tinnitus occurred approximately 4-6 weeks following neurosurgery for gross total excision of space-occupying lesions of the cerebellopontine angle and hearing was lost in the operated ear. In both cases, the gaze-evoked tinnitus was characterized as being tonal in nature, with pitch and loudness percepts remaining constant as long as the same horizontal or vertical eye directions were maintained. Tinnitus was absent when the eyes were in a neutral head-referenced position with subjects looking straight ahead. The results and implications of ophthalmological, standard and modified visual-field assessment, pure-tone audiometric assessment, spontaneous otoacoustic emission testing and detailed psychophysical assessment of pitch and loudness are discussed.

The disconnected ear: phenomenological effects of a large acoustic tumor.

OBJECTIVE: To document the existence of a peripheral auditory disconnection syndrome in a 23-yr-old male with a large tumor of the right cerebellopontine angle using contemporary behavioral, electroacoustic, and electrophysiologic auditory tests. DESIGN: Single subject with repeated measures. RESULTS: In spite of a profound hearing loss in an ear with a large cerebellopontine angle tumor determined by behavioral audiometry, distortion product otoacoustic emissions, surface recorded brain stem auditory evoked potentials, and transtympanic electrocochleography (click evoked compound action potentials and tone evoked cochlear microphonics) demonstrated that the cochlea was intact and functional over a broad bandwidth and intensity range. CONCLUSIONS: A peripheral auditory disconnection syndrome is demonstrated in a 23-yr-old male with a large tumor of the cerebellopontine angle. In this instance, the tumor effectively deafferentated the peripheral from central auditory nervous system, resulting in profound hearing loss of presumed neural origin. It is suggested that other pathologic conditions/mechanisms could produce similar findings.