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Bilateral vestibular failure is a rare, often unrecognised, clinical entity (0.6%–2% of all routinely performed electronystagmography), characterised by unsteadiness of gait and oscillopsia during head movements.1 The unsteadiness is due to loss of the vestibulospinal reflexes. It increases in darkness or when walking on uneven or soft ground—that is, when visual and somatosensory inputs, necessary for vestibular substitution, get compromised. Oscillopsia is an illusory movement of a stationary surrounding which occurs typically during locomotion as a result of a retinal slip due to an insufficient vestibulo-ocular reflex. The diagnosis of bilateral vestibular failure can be supported clinically by the finding of an abnormal visuo-ocular reflex (doll's eyes), and an abnormal gaze fixation with compensatory saccades during rapid head turns (the head thrust test). A bithermal caloric test or a rotational chair test confirms the diagnosis by demonstrating the absence of vestibular responses.1
Ototoxic drugs (for example, aminoglycosides) are the most common cause of bilateral vestibular failure, followed by sporadic multisystem degeneration, infectious meningitis, bilateral cerebellopontine angle tumours, and autoimmune disorders. Neuropathies (such as vitamin B12 deficiency, hereditary polyneuropathies, and sarcoidosis), sequential vestibular neuronitis, and bilateral Menière's disease also often lead to bilateral vestibular failure.1-3 Bilateral vestibular failure due to leptomeningeal metastasis has been reported to occur as a part of the clinical picture of carcinomatous meningitis, including symptoms of increased intracranial pressure, multiple cranial and spinal nerve involvement, and changes in mental state.1 3 4 We report on a patient with carcinoma of the breast where rapidly progressive bilateral vestibular failure was the main and outstanding presenting symptom of leptomeningeal spread.
A 73 year old woman was admitted because of progressive gait unsteadiness, bilateral tinnitus, and headache for 2 months. Her history comprised ischaemic heart disease, hypertension, familial tremor, and left Bell's palsy 10 years previously. In 1995 she was operated on for breast carcinoma. Two years later metastasis to the axilla was treated with chemotherapy.
On admission the patient complained about bilateral tinnitus, more on the right, and severe unsteadiness of gait, up to inability to walk without aid. When sitting or lying she had no coordination problems. Examination disclosed an old left peripheral facial palsy with pathological synkinesias. The eyes were aligned in all gaze directions and their range of movement was full. There was no primary position, nor gaze evoked nystagmus by observation or while wearing Frenzel's glasses. When performing the doll's eyes test a broken vestibulo-ocular reflex was obtained. The head thrust test demonstrated corrective saccades during head rotation to either side. The visual dynamic acuity test performed by reading a Jaeger's chart while oscillating the head of the patient at a frequency of 1 Hz,1 showed a drop of four lines of visual acuity, compared with the visual acuity while the head was static. These findings were indicative of vestibulo-ocular reflex insufficiency. No papilloedema or pyramidal signs were found. The ankle reflexes were absent and sensation to pinprick was decreased up to the ankles; the position and vibration sense were normal. Cerebellar functions were preserved, as judged by the finding of a normal smooth pursuit and saccades of eye movements, as well as finger-nose and heel-knee testing. When standing, the patient tended to fall backwards and was unable to stand with her eyes closed. Her gait was severely atactic, without any side preference.
T1 and T2 weighted MRI of the brain with gadolinium disclosed a bilateral abnormal enhancement of the VIIIth cranial nerves in the region of the internal acoustic canal, compatible with an inflammatory or infiltrative process of the nerve (fig 1 ).
Electronystagmography showed bilateral caloric weakness of 100%. Ocular motility was within normal limits. No spontaneous, gaze evoked, or positional nystagmus was recorded. A dynamic posturography showed a combined vestibular more than visual pattern of instability. Pure tone audiometry, performed 2 months earlier, had shown a bilateral sensorineural hearing loss of 40 dB in all frequencies, with normal speech discrimination. Repeated audiometric testing showed a plateau decrease of 50 dB in both ears and decreased speech discrimination of 75% in the right ear (normal>90% ), indicative of retrocochlear nerve involvement.
On lumbar puncture a clear CSF with 160 mm H2O opening pressure (normal 100–200 mm H2O) was obtained. Laboratory analysis of CSF showed 31 epithelial carcinomatous cells/mm3, increased protein content of 121 mg% (normal<50 mg %) and borderline low glucose content of 49 mg/d blood glucose concentration (normal>50 mg/d). Carcinoembryonic antigen (CEA) was raised (16.8 μg/l, normal<10 μg/l ).
A six course therapy with intrathecal methotrexate was started: 12.5 mg of methotrexate were administered once every 2 weeks, followed by oral leucovorin (30 mg every 4 hours) on the next day. Ten weeks after the start of therapy the patient's state remained unchanged and 22 weeks later she died.
Hearing loss as the first manifestation of carcinomatous meningitis was reported in five patients by Alberts et al.4 In all but one of their patients other associated neurological findings were present, indicative of widespread meningeal involvement by the time of cochlear manifestation. Neuro-otological testing performed on three patients disclosed bilateral caloric weakness in two. However, neither of these patients was reported to have vestibular symptoms. Other authors have described ataxia and hearing loss as the presenting symptom of carcinomatous meningitis.5 Nevertheless, in most of the reports, no conclusions were made as to whether the ataxia was due to hydrocephalus, cerebellar carcinomatous involvement, spinal cord compression, metastatic destruction of the pyramidal bone, or if it was the result of vestibular nerve infiltration. Moreover, neuro-otological testing was usually not performed.
The spread of neoplastic cells to the meninges occurs either directly from an adjacent tumour, or from distant primary tumours by the blood stream, or perivascular or perivenous lymphatics.5Pathological examination shows that neoplastic cells extend in the temporal bone as far as the geniculate ganglion, where the subarachnoid space terminates, but can penetrate the cribriform area of the labyrinth. Labyrinthine metastasis of the tumour is a common finding, whereas selective internal auditory canal infiltration, as in our patient, is rare5.
The proximity of the VIIth and VIIIth nerves in the internal auditory canal makes both of them vulnerable to pathological changes in this location. Indeed, from the 15 patients with carcinomatous meningitis and labyrinthine involvement reported by Oshiro et al, unilateral or bilateral facial nerve palsy was documented in nine5 Our patient had an old facial palsy after viral infection 10 years previously. Recent damage, such as by neoplastic cell involvement, would have probably abolished the facial synkinesias— evidence of a long standing, partly regenerated nerve lesion.
The syndrome of bilateral vestibular failure consists of gait unsteadiness and oscillopsia. The severe instability of stance in our patient might have been due to a polyneuropathy induced by the cancer or chemotherapy, even though gross proprioception defects were not detected on clinical testing. Our patient did not complain about oscillopsia or other visual phenomena attributable to vestibular failure. As patients with bilateral vestibular failure have impaired perception of motion, oscillopsia is perceived less than the real retinal image slip and 30%–40% of patients with bilateral vestibular failure never complain about this visual phenomenon.1 6
Infectious meningitis is not rare among the multiple causes of bilateral vestibular failure.1 2 However, carcinomatous meningitis is encountered much less and here bilateral vestibular failure is usually a part of a syndrome of meningeal infiltration with multiple cranial and spinal nerve involvement, hydrocephalus, or cerebral changes.3-5 In our patient the vestibulocochlear nerves were selectively involved. The only other symptom suggestive of meningitis was her complaint about a diffuse headache. Although patients with vestibular lesions often report headache, this is usually located in the neck and probably results from disturbed vestibulocollic reflexes.1
Carcinomatous meningitis is encountered in the course of metastatic breast cancer in 1%–3.5% of patients.3 Intrathecal administration of methotrexate, radiotherapy, or the combination of both, are today the treatment options, but the optimal treatment has not been established and is individual for each patient. Despite aggressive therapy, most patients die within 6 months of diagnosis, the median survival being 6–16 weeks.7 It has been reported that response after 2 weeks of therapy is correlated with survival.7 Unfortunately, our patient did not respond to therapy.
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