Ocular vestibular evoked myogenic potentials induced by air-conducted sound in patients with acute brainstem lesions

ObjectiveThe ocular vestibular-evoked myogenic potential (oVEMP), a recently documented otolith-ocular reflex, is considered to reflect the central projections of the primary otolithic afferent fibers to the oculomotor nuclei. The aim of our study is to define air-conducted sound oVEMP abnormality in patients with acute brainstem lesions and to determine the brainstem structures involved in the generation of oVEMPs.MethodsIn response to air-conducted tone burst sounds (ACS), oVEMP was measured in 52 patients with acute brainstem lesions. Individualized brainstem lesions were analyzed by means of MRI-based voxel-wise lesion-behavior mapping, and the probabilistic lesion maps were constructed.ResultsMore than half (n = 28, 53.8%) of the patients with acute brainstem lesions showed abnormal oVEMP in response to ACS. The majority of patients with abnormal oVEMPs had lesions in the dorsomedial brainstem that contains the medial longitudinal fasciculus (MLF), the crossed ventral tegmental tract (CVTT), and the oculomotor nuclei and nerves.ConclusionMLF, CVTT, and the oculomotor nuclei and nerves appear to be responsible for otolith-ocular responses in the brainstem.SignificanceComplemented to cervical VEMP for the uncrossed otolith-spinal function, oVEMP to ACS may be applied to evaluate the crossed otolith-ocular function in central vestibulopathies.     

Wallenberg's syndrome: lateropulsion, cyclorotation, and subjective visual vertical in thirty-six patients.

We measured the subjective visual vertical, cyclorotation of the eyes, and head and body lateropulsion in 36 patients with Wallenberg's syndrome. All patients exhibited significant tilts of the internal representation of the gravity vector, as indicated by deviation of subjective visual vertical ipsiversive to the lesion. Most patients (82%) had ipsiversive cyclorotation of one or both eyes, especially excyclotropia of the eye ipsilateral to the brainstem lesion. Twelve of 36 patients (33%), those with the most severe body lateropulsion, had a complete ocular tilt reaction consisting of head tilt, skew deviation, and cyclorotation in the roll plane. We hypothesize that deviation of subjective visual vertical, lateropulsion of the body, and cyclorotation of the eyes are the perceptual, the ocular motor, and the postural consequences of a common lesion of central vestibular pathways that subserve the vestibuloocular reflex in the roll plane. Lateropulsion in patients with Wallenberg's syndrome is interpreted as a postural consequence of an abnormal tilt of the internal representation of orientation in space.     

Acquired pendular nystagmus: its characteristics, localising value and pathophysiology

Investigations were made of 16 patients with acquired pendular nystagmus and a further 32 cases reported in the literature were reviewed. Amongst our own patients two thirds had multiple sclerosis, almost one third a cerebrovascular accident or angioma and two had optic atrophy with squint. The nystagmus took forms which could be monocular or binocular, conjugate or disconjugate and could involve movements about single or multiple axes. Spectral analysis was used to characterise the amplitude and frequency of the movements and to estimate the degree of relationship (coherence) between movements of the two eyes or between movements of one eye about several axes. The oscillations ranged in frequency from 2·5 Hz to 6 Hz, with typical amplitudes between 3° and 5°. In a given patient all oscillations, regardless of plane, were highly synchronised. Somatic tremors of the upper limb, face and palate associated with the nystagmus were often at similar frequencies to the eye movement. The other ocular signs common to all our patients were the presence of squint with failure of convergence. Most patients also had skew deviation or internuclear ophthalmoplegia or both. The major oculomotor systems, that is, saccades, pursuit, optokinetic and vestibulo-ocular reflexes could be intact. It is inferred that the mechanism responsible for the pendular nystagmus lies at a level which is close to the oculomotor nuclei so that it can have monocular effects but is not part of the primary motor pathways. It is possible that this mechanism normally subserves maintenance of conjugate movement and posture of the eyes. The periodicity of the nystagmus is likely to arise from instability in a certain type(s) of neurone, for the associated somatic tremors have similar characteristics and yet involve very different neuronal muscular circuitry. Prognosis for cessation of the nystagmus is poor. In five patients with multiple sclerosis it was suppressed by intravenous hyoscine with, however, unacceptable subsequent side effects.     

Visuospatial disorders and related lesions of the brain

Ten right-handed patients suffering from visuospatial impairment were examined. The impairment was ascertained by a test requiring visual organization (picture completion). The patients did not suffer from other neuropsychological disorders (e.g., aphasia, dementia). Furthermore, psychiatric symptoms and defective oculomotion (gaze paresis, ocular paresis) were controlled. CT scan data revealed that in 4 patients the impairment was associated with lesions of the posterior right hemisphere. All lesions involved the central optic pathways and were accompanied by visual field defects. On the other hand, 6 patients turned out as suffering from damage of the cerebellum or brainstem. The available electronystagmographical data revealed impaired visual fixation, an oculomotor defect characterizing gaze apraxia, the diagnostic marker of Balint's syndrome.     

Midbrain arteriovenous malformation causing bilateral total ophthalmoplegia as an initial ocular symptom--a case report

A 61-year-old woman is presented with a bilateral total ophthalmoplegia as an initial ocular symptom, caused by a midbrain hematoma. She complained of acute headache, nausea, vomiting and bilateral closure of her eyelids. Examination on admission showed meningeal irritation; mild consciousness disturbance; bilateral total ophthalmoplegia; left hemiparesis; ataxia in all extremities, more marked to the left. Computed tomography demonstrated a small hematoma in the midbrain tegmentum. Angiography demonstrated midbrain arteriovenous malformation, and she was treated conservatively. Abduction of both eyes and adduction of the left eye appeared on the next day of the ictus, and after that, improved gradually. Left ptosis had improved since one week after the ictus. Light reflex of the left pupil had seen 5 days after the ictus. At the same time, the left pupil revealed an oval-shape. Right internal ophthalmoplegia continued to exist. One year later, the right eye deviated externally, and the left deviated inferio-medially. Abduction of both eyes was normal. Infraduction of both eyes was seen, but limited on the left. Upgaze paresis remained unchanged, and adduction of the right eye was absent. Adduction of the left eye showed almost full recovery. There was right complete ptosis, but left ptosis became indefinite. These ocular findings indicated typical right oculomotor paresis plus superior rectus paresis of the left eye, which suggested a destructive lesion in the right oculomotor nucleus. Also, her left extremities showed a hemiparesis as a pyramidal tract sign (Weber's syndrome) and an ataxia as a cerebellar sign (Claude's syndrome).(ABSTRACT TRUNCATED AT 250 WORDS)     

A case of transient bilateral primary oculomotor nerve paresis associated with head injury

A 13-year-old boy, with no past medical history, was admitted after a car accident on October 29, 1989. On admission, he was alert. Physical examination revealed a bruise on the left frontal region, a fracture of right clavicula and right hemopneumothorax. He was treated with respirator due to dyspnea. On November 1, 1989, he was removed from respirator and expressed diplopia. Neurological examination showed bilateral ptosis, mild anisocoria, normal light reflex and horizontal gaze nystagmus in lateral gaze. Both eyes were deviated outward slightly in the primary position and showed inability to converge. The external ocular movements of both eyes were mildly limited in elevation and adduction. Ataxia was observed in bilateral upper extremities. Deep reflexes were normal and no pathological reflexes were observed. Brain CT scans showed no abnormality. On November 6, 1989, his ptosis and diplopia improved. On November 8, he was completely recovered. A magnetic resonance imaging on November 10 revealed no abnormality. We suggested that transient dysfunction of midbrain associated with head injury might cause transient bilateral primary oculomotor nerve paresis, nystagmus and ataxia.     

Vestibular syndromes in the roll plane: Topographic diagnosis from brainstem to cortex

Central vestibular syndromes may be classified according to the three major planes of action of the vestibuloocular reflex, secondary to a lesional tone imbalance in either the horizontal yaw plane or the vertical pitch or roll plane. The clinical signs, both perceptual and motor, of a vestibular tone imbalance in the roll plane are ocular tilt reaction (OTR), ocular torsion, skew deviation and tilts of the perceived visual vertical (SVV). Either complete OTR or skew torsion without head tilt indicates a unilateral peripheral deficit of otolith input or a unilateral lesion of graviceptive brainstem pathways from the vestibular nuclei (crossing midline at the pontine level) to the interstitial nucleus of Cajal (INC) in the rostral midbrain. SVV tilts are the most sensitive sign of a vestibular tone imbalance in roll and occur with peripheral or central vestibular lesions from the labyrinth to the vestibular cortex. All tilt effects, perceptual, ocular motor and postural, are ipsiversive (ipsilateral eye undermost) with unilateral peripheral or pontomedullary lesions below the crossing of the graviceptive pathways. All tilt effects are contraversive (contralateral eye undermost) with unilateral pontomesencephalic brainstem lesions and indicate involvement of the medial longitudinal fasciculus or the rostral midbrain (INC). Unilateral lesions of vestibular structures rostral to the INC typically manifest with deviations of perceived vertical without concurrent eye–head tilt. OTR in unilateral paramedian thalamic infarctions indicates simultaneous ischemia of the paramedian rostral midbrain including the INC. Unilateral lesions of the posterolateral thalamus can cause thalamic astasia and moderate ipsiversive or contraversive SVV tilts, thereby indicating involvement of the vestibular thalamic subnuclei. Unilateral lesions of the parietoinsular vestibular cortex cause moderate, mostly contraversive SVV tilts. An SVV tilt found with monocular but not with binocular viewing is typical for a trochlear or oculomotor palsy rather than a supranuclear graviceptive brainstem lesion.     

Crossed innervation of the superior rectus.

We studied two patients which showed a paralysis of the oculomotor nerve on one side and isolated paralysis of the superior rectus on the other side. On the side of oculomotor nerve paralysis, midbrain infarct extending from the paramedian tegmentum to crus cerebri was demonstrated in one case who showed no recovery, and a small lacuna in midbrain tegmentum in another one who showed complete recovery. On the side of isolated paralysis of the superior rectus, no lesion was demonstrated by CT and MRI, and no clinical signs of the involvement of fiber tracts or nuclei were evident in both cases. A unilateral lesion of oculomotor nerve nucleus caused a paralysis of the contralateral superior rectus.     

A modification of eye-head coordination by CNS disease

When a subject, seated and facing ahead, was asked to look toward one side, the result was a combined movement of the eyes and head. Normal subjects began the eye movement just before the onset of head movement; 4 neurologic patients who showed abnormalities in eye movements (saccades that tended to be smaller in amplitude and lower in velocity than those of the control subjects) regularly began eye movement after the onset of head movement. Thus the initiation of head rotation was not as much retarded in these patients as that of eye movement. Amplitudes of the movements were reduced in the patients, but this change too was less for the head than for the eyes.Because the amplitude and velocity of the head movement were less affected in the patient group, the relative contribution of the head to the total gaze shift was increased.It appears as if, when the oculomotor system is affected, the head can assume a leading role in the initiation and execution of gaze shifts.     

A case of "ping-pong ball eye movement (author's transl)]

We experienced a rare and peculiar eye movement in a comatose patient with ruptured intracranial aneurysm. The patient's eyes moved quickly and irregulary from one extreme position to the other with whirling and bounding components. Such abnormal eye movement occasionally halted, but abruptly reappeared. We named this abnormal eye movement which had never been reported before, "ping-pong eye movement". Neuropathological study revealed a subarachnoid hemorrhage and the diffuse infarction in the right remporal lobe, and a smal clot in the fourth ventricle without specific findings in the brainstem and the cerebellum. Consideration was made that the hemorrhage in the fourth ventricle resulted in a hyper-irritable state in the fastigial nuclei, from which the abnormal discharges were driven to the reticular formation, the vestibular nuclei, the MLF, and the oculomotor complexes. We conclude that this "ping-pong" ball eye movement" might be the appearance of epilepsy in the eyes, due to the epileptogenic focus of the fastigial nuclei.     

Ocular counterrolling abnormalities in spasmodic torticollis

Spasmodic torticollis is a focal dystonic movement disorder of unknown origin, long hypothesized to have some vestibular involvement. An examination of otolith function, ocular counterrolling, was performed on eight patients with this disorder. The test consisted of photographing both eyes while the subject underwent rotation in both naso-occipital and earth-horizontal long axes. Measurements of eye torsion were made with a superimposition technique accurate to 0.1 degrees. Results showed all eight patients had abnormal ocular counterrolling. The most notable defect was the lack of sustained eye torsion at the extreme positions, resulting in rolling of the eyes in the direction of head tilt rather than counterrolling, a phenomenon previously observed only in persons with known brain-stem problems. That finding, as well as the majority of the patients showing spontaneous vestibular nystagmus in the dark and directional preponderance with caloric stimulation, implies that one difficulty in spasmodic torticollis lies in central vestibular connections, manifested by disruption of brain-stem pathways.     

Strabismus and Micro-Opsoclonus in Machado-Joseph Disease

We describe novel deficits of gaze holding and ocular alignment in patients with spinocerebellar ataxia type 3, also known as Machado-Joseph disease (MJD). Twelve MJD patients were studied. Clinical assessments and quantitative ocular alignment measures were performed. Eye movements were quantitatively assessed with corneal curvature tracker and video-oculography. Strabismus was seen in ten MJD patients. Four patients had mild to moderate intermittent exotropia, three had esotropia, one had skew deviation, one had hypotropia, and one patient had moderate exophoria. Three strabismic patients had V-pattern. Near point of convergence was normal in two out of three patients with exotropia. Gaze holding deficits were also common. Eight patients had gaze-evoked nystagmus, and five had micro-opsoclonus. Other ocular motor deficits included saccadic dysmetria in eight patients, whereas all had saccadic interruption of smooth pursuit. Strabismus and micro-opsoclonus are common in MJD. Coexisting ophthalmoplegia or vergence abnormalities in our patients with exotropia that comprised 50 % of the cohort could not explain the type of strabismus in our patients. Therefore, it is possible that involvement of the brainstem, the deep cerebellar nuclei, and the superior cerebellar peduncle are the physiological basis for exotropia in these patients. Micro-opsoclonus was also common in MJD. Brainstem and deep cerebellar nuclei lesion also explains micro-opsoclonus, whereas brainstem deficits can describe slow saccades seen in our patients with MJD.     

Neurophysiolgical analysis in an 18-month-old girl with Gaucher's disease type 2

Gaucher's disease is caused by a lack of glucocerebrosidase, and in type 2 various neurological symptoms can occur;however, the detailed pathogenesis of the condition remains undetermined. Here we performed neurophysiological examinations in an 18-month-old girl with Gaucher's disease type 2 to specify the brainstem lesions. Developmental delay occurred from the age of 8 months, and the patient subsequently showed strabismus, loss of head control, failure to thrive and irregular respiration. She was admitted to our hospital at the age of 18 months. A definite diagnosis of Gaucher's disease type 2 was made from the presence of Gaucher cells and reduced glucocerebrosidase activity. Clinically, limited ocular movements, poor facial expression and bulbar palsy indicated disturbances in the nuclei of oculomotor, trochlear, abducent, facial and ambiguous nerves, although magnetic resonance imaging (MRI) failed to visualize any structural changes in the brain including the brainstem. Neurophysiologically, auditory brainstem response and somatosensory evoked potential demonstrated lesions in the cochlear nucleus and medial lemniscus, respectively. On polysomnography, disturbed sleep parameters during rapid eye movement sleep, in addition to the lack of modification of respiratory patterns by sleep stage, suggested dysfunctions in the locus ceruleus, raphe nuclei and pontine reticular formations. It is likely that these neurophysiological tests can be useful to identify functional lesions that are not detectable by MRI, and should help exploit new treatments for child-onset neurodegenerative disorders such as Gaucher's disease.     

Fast eye movement initiation of ocular torsion in mesodiencephalic lesions

Three patients with episodic ocular torsion and skew deviation due to mesodiencephalic lesions were studied by using binocular three-dimensional scleral search coils. The conjugate ocular torsion (upper pole of each eye rotating toward the side of the brainstem lesion) was initiated by a torsional fast eye movement. During prolonged episodes, torsional nystagmus was also present. Cessation of the ocular torsion and skew deviation occurred by slow eye movements with exponentially decreasing velocities in 2 patients, and by multiple fast torsional movements in 1 patient. In 1 patient, the abnormal eye movements were temporally linked to dystonic movements in the limbs on the side opposite the brainstem lesion. The occurrence of skew deviation with conjugate ocular torsion in brainstem lesions has been attributed to functional asymmetry in vestibular pathways responsible for the slow-phase compensatory eye movement response to roll. In comparison, the findings in our patients show that in mesodiencephalic lesions conjugate ocular torsion with skew deviation may be generated by torsional fast eye movements, indicating activation of the burst cells of the rostral interstitial nucleus of the medial longitudinal fasciculus.     

Skew deviation with ocular torsion: A vestibular brainstem sign of topographic diagnostic value

Fifty-six patients with unilateral brainstem infarctions presenting with skew deviation of the eyes were analyzed for static vestibular function in the roll plane. Ischemic lesions were allocated to the level and side of the brainstem by the clinical syndrome and neuroimaging. Two findings of clinical relevance were obtained: (1) All skew deviations were ipsiversive (ipsilateral eye was undermost) with caudal pontomedullary lesions and contraversive (contralateral eye was lowermost) with rostral pontomesencephalic lesions. (2) All skew deviations were associated with concomitant ocular torsion and tilts of subjective visual vertical toward the undermost eye. Thus, skew deviation or more correctly, ocular skew torsion is a sensitive brainstem sign of localizing and lateralizing value. Evidence is presented that the ocular skew torsion sign indicates a vestibular tone imbalance in the roll plane secondary to graviceptive pathway lesions.     

Alternating skew deviation: 47 patients

Of 408 patients with ocular skew deviation, 47 (12%) had hypertropia that alternated on gaze to either side. Pretectal lesions were responsible for 29 cases, and lower brainstem signs were seen in 5; the site of posterior fossa involvement was uncertain in 13. Acute hydrocephalus, tumors, strokes, and MS were the most frequent causes, followed by spinocerebellar degeneration and tentorial herniation. The mechanism of alternating skew is unknown, but probably involves pathways from both utricles to the vertical-rotatory ocular motor neurons.     

Differential vulnerability of oculomotor, facial, and hypoglossal nuclei in G86R superoxide dismutase transgenic mice

In recent years, several mouse models of amyotrophic lateral sclerosis (ALS) have been developed. One, caused by a G86R mutation in the superoxide dismutase-1 (SOD-1) gene associated with familial ALS, has been subjected to extensive quantitative analyses in the spinal cord. However, the human form of ALS includes pathology elsewhere in the nervous system. In the present study, analyses were extended to three motor nuclei in the brainstem. Mutant mice and control littermates were evaluated daily, and mutants, along with their littermate controls, were killed when they were severely affected. Brains were removed after perfusion and processed for Nissl staining, the samples were randomized, and the investigators were blinded to their genetic status. Stereologic methods were used to estimate the number of neurons, mean neuronal volumes, and nuclear volume in three brainstem motor nuclei known to be differentially involved in the human form of the disease, the oculomotor, facial, and hypoglossal nuclei. In the facial nucleus, neuron number consistently declined (48%), an effect that was correlated with disease severity. The nuclear volume of the facial nucleus was smaller in the SOD-1 mutant mice (45.7% difference from control mice) and correlated significantly with neuron number. The oculomotor and hypoglossal nuclei showed less extreme involvement (<10% neuronal loss overall), with a trend toward fewer neurons in the hypoglossal nucleus of animals with severe facial nucleus involvement. In the oculomotor nucleus, neuronal loss was seen only once in five mice, associated with very severe disease. There was no significant change in the volume of individual neurons in any of these three nuclei in any transgenic mouse. These results suggest that different brainstem motor nuclei are differentially affected in this SOD-1 mutant model of ALS. The relatively moderate and late involvement of the hypoglossal nucleus indicates that, although the general patterns of neuronal pathology match closely those seen in ALS patients, some differences exist in this transgenic model compared with the progression of the disease in humans. However, these patterns of cellular vulnerability may provide clues for understanding the differential susceptibility of neural structures in ALS and other neurodegenerative diseases.     

Specificity of "peering at the tip of the nose" for a diagnosis of thalamic hemorrhage

BACKGROUND: Tonic inward and downward deviation of the eyes ("peering at the tip of the nose") is regarded as a unique feature of thalamic hemorrhage, but the mechanisms of this ocular finding remain obscure. OBJECTIVES: To describe 4 patients who showed tonic inward and downward deviation of the eyes from brainstem or thalamic lesions and to discuss the possible mechanisms involved. DESIGN: Case report. SETTING: Secondary and tertiary referral hospitals. RESULTS: One patient developed alternating esotropia with downward ocular deviation from thalamic hemorrhage compressing the midbrain. Two patients showed multiple infarctions in the territory of the posterior circulation with or without the involvement of the thalamus. Another patient had lateral pontine hemorrhage extending up to the midbrain tegmentum. Ocular bobbing preceded or accompanied tonic ocular deviation in 3 patients. CONCLUSIONS: Tonic inward and downward deviation of the eyes may develop in thalamic or brainstem lesions. Irritation or destruction of the neural structures involved in the vergence and vertical gaze may cause this ocular sign in mesodiencephalic lesions. Skew deviation and esotropia from abduction deficit may be involved in some patients. Ocular bobbing and tonic downward deviation may share a common pathogenesis.     

Slowly alternating skew deviation: Description of a pretectal syndrome in three patients

Three patients who had slowly alternating skew deviation are described: each had elements of the Sylvian aqueduct syndrome. This combination of signs supports a pretectal location for lesions associated with alternating skew movements. Postmortem examination of a patient who died of chronic herpes simplex encephalitis showed extensive demyelination and periaqueductal spongiform degeneration; there was preservation of the oculomotor and trochlear nuclei, the medial longitudinal fasciculus, vestibular nuclei, and the interstitial nucleus of Cajal bilaterally. The slowly alternating dysconjugate vertical movements bear a resemblance to both see-saw nystagmus and the ocular tilt response.     

Oculomotor and vestibular findings in autosomal recessive spastic ataxia of Charlevoix-Saguenay.

Electronystagmographic recordings were made of oculomotor and vestibular function in 11 patients with autosomal recessive spastic ataxia of Charlevoix-Saguenay. All had horizontal gaze nystagmus, marked impairment of smooth ocular pursuit and optokinetic nystagmus, and defective fixation suppression of caloric nystagmus. Many had saccadic dysmetria, but saccade velocity was probably unaffected. Abnormalities pointing to brainstem disturbance were sparse. The findings are thought to indicate mainly diffuse cerebellar disease, with particular involvement of vermis and vestibulo-cerebellum.