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Biomedical subjects

G M Halmagyi

Publications and source records attributed to G M Halmagyi.

At least 109 records · Page 6Linked to original sources
PubMed1989

Linear acceleration perception in the roll plane before and after unilateral vestibular neurectomy.

The ability of 33 patients to perceive the direction, relative to the body long axis, of a linear acceleration vector acting in the coronal plane, roll-tilt perception, was studied at various times, before and from 1 week to 6 months after unilateral, selective vestibular neurectomy for Meniere's disease, acoustic neuroma or intractable paroxysmal vertigo. The results of these patients were compared with the results of 31 normal subjects and two control patients who had both vestibular nerves surgically sectioned. Rotating on a fixed-chair centrifuge in an otherwise darkened room, each observer was required to indicate his perception of the direction of the resultant gravito-inertial vector by setting a small, motor-driven, illuminated bar, attached to the chair but rotatable in the fronto-parallel plane, to the perceived gravitational horizontal. Normal subjects accurately align the bar with respect to the gravito-inertial resultant vector which, in the dark, they assume to be the gravitational vertical. This percept has been called the oculogravic illusion. Accurate roll-tilt perception is due to vestibular (probably mainly otolithic) sensory information since patients with bilateral vestibular neurectomies do not perceive the resultant vector accurately. Whereas normal subjects perceive resultant vectors directed to the right and to the left equally accurately, roll-tilt perception was invariably asymmetrical one week after unilateral vestibular neurectomy. Even at rest there was an asymmetry in the baseline settings, so that patients set the bar down on the side of the operated ear, in order for it to appear gravitationally horizontal: if a patient had a right vestibular nerve section then he set the bar clockwise (from the patient's view) below the true gravitational horizontal. With increasing gravito-inertial resultant angles there was an increasing asymmetry of roll-tilt perception due both to decreased sensitivity to roll-tilt stimuli directed towards the operated ear and to transiently increased sensitivity to roll-tilt stimuli directed towards the intact ear. A progressive decrease in both perceptual asymmetries followed, rapidly in the first 3 weeks, more slowly in the next 6 months.(ABSTRACT TRUNCATED AT 400 WORDS)

Acceleration↗
PubMed1988

A clinical sign of canal paresis.

Unilateral loss of horizontal semicircular canal function, termed canal paresis, is an important finding in dizzy patients. To our knowledge, apart from head-shaking nystagmus, no clinical sign of canal paresis has yet been described and the term derives from the characteristic finding on caloric tests: little or no nystagmus evoked by either hot or cold irrigation of the affected ear. We describe a simple and reliable clinical sign of total unilateral loss of horizontal semicircular canal function: one large or several small oppositely directed, compensatory, refixation saccades elicited by rapid horizontal head rotation toward the lesioned side. Using magnetic search coils to measure head and eye movement, we have validated this sign in 12 patients who had undergone unilateral vestibular neurectomy.

Eye Movements↗
PubMed1985

Paraneoplastic cerebellar disease. Remission with excision of the primary tumor.

We describe two patients with paraneoplastic cerebellar syndromes who gained clinically useful neurologic remissions following radical excision of the primary cancer. In both patients the syndrome was characterized by the rapid onset of gait ataxia, nausea, postural vertigo, central positional nystagmus, and saccadic oscillations. These observations encourage radical treatment of the primary cancer in patients with advanced malignant neoplasms who are disabled by cerebellar dysfunction, and lend support to a current hypothesis that paraneoplastic cerebellar degeneration is due to anticerebellar Purkinje cell antibodies elaborated by the primary cancer.

Adenocarcinoma↗
PubMed1985

Focal seizures: an unusual presentation of giant intracranial aneurysms. A report of four cases with comments on the natural history and treatment.

Four patients with partial epileptic seizures for several years, but without permanent neurological deficits, were found to have giant aneurysms of the middle cerebral artery. None had a history of subarachnoid hemorrhage. Operative findings included compression of the medial temporal and subfrontal cortex, infarction of the superior temporal gyrus, and evidence of previous hemorrhage from the aneurysms. In two patients, clipping of the aneurysm with decompression of the adjacent temporal lobe cured the seizure disorder. In the other two patients, the aneurysms could only be wrapped, and the seizures continued. It is postulated that focal compression of temporal lobe structures and local hemodynamic phenomena caused by the giant aneurysm predispose to epilepsy in these patients.

Epilepsies, Partial↗
PubMed1983

Downbeating nystagmus. A review of 62 cases.

We reviewed the clinical and oculomotor findings in 62 patients with downbeating nystagmus (DBN). Only those patients whose DBN was enhanced in lateral gaze were included. Apart from gait ataxia, few patients had additional neurologic signs. The two most common causes of DBN were cerebellar ectopia (25%) and cerebellar degeneration (25%) with another 10% having a variety of conditions. In about 40% the cause remained undiagnosed. In some patients with idiopathic DBN and in others with DBN due to cerebellar ectopia, the disease progressed slowly, if at all. In DBN the slow-phase velocity is dependent on vertical head position and head velocity in pitch; vertical pursuit, particularly downward pursuit, is defective and vertical vestibulo-ocular reflexes are intact. We concluded that at least some cases of DBN were due to an imbalance in otolithocular reflexes. The lesion causing DBN appears to be in the vestibulocerebellum, perhaps the nodulus, a structure that normally inhibits otolith-ocular reflexes.

Adolescent↗
PubMed1983

Eye blink reflexes to sudden free falls: a clinical test of otolith function.

Conventional neuro-otological tests measure only semi-circular canal function and not otolith function. A clinically acceptable test of otolith function was developed. Previous studies suggested that muscle responses which occur less than 100 ms after release into free-fall are part of a startle reflex originating in the otoliths. With a couch capable of producing sudden, safe, comfortable free-falls it was shown that in normal subjects orbicularis oculi muscle responses (that is eyeblinks) invariably began within 45 ms of this stimulus and confirmed that these eyeblink reflexes are part of a generalised startle reflex, as they cross-habituate with eyeblink reflexes elicited by supraorbital nerve stimulation. Eyeblink reflexes to free-fall may prove a useful clinical test of otolith function.

Adult↗
PubMed1982

Spontaneous thrombosis of a giant intracranial aneurysm and ipsilateral internal carotid artery. Case report.

Computerized tomography revealed a thrombosed giant intracavernous carotid aneurysm in a man who presented with ophthalmoplegia and headache. Angiography confirmed complete aneurysmal thrombosis and also revealed complete occlusion of the ipsilateral internal carotid artery. Aneurysmotomy and thrombectomy produced substantial reduction in mass effect, with symptomatic improvement. The spontaneous thrombosis of giant intracranial aneurysms is discussed.

Adult↗
PubMed1981

Tremor, the cogwheel phenomenon and clonus in Parkinson's disease.

Resting and postural tremor, intention and action tremor, clonus and the cogwheel phenomenon in Parkinson's disease have been characterised in terms of frequency content using spectral analysis. Typical resting tremor ranged in peak frequency from 4 to 5.3 HZ with tremor in each individual varying only by 0.2 to 0.3 HZ. The peak frequency of postural tremor ranged between 6 and 6.2 HZ. Intention tremor appeared to be an exaggeration of postural tremor. Clonus evoked by active or passive stretch at the wrist had a frequency of 6 HZ and appeared to be a continuation of postural tremor. The cogwheel phenomenon was found at frequencies between 6 and 6.5 HZ and between 7.5 to 9 HZ. Action tremor was indistinguishable from the cogwheel phenomenon. Some patients had either a symptomatic resting tremor with a concurrent 6 HZ component of smaller amplitude or a symptomatic postural tremor with a 4-5 HZ component of smaller amplitude. These combinations would produce two peaks in the power spectrum. When this occurred EMG studies showed that individual muscles had two types of rhythmical activation suggesting that the tremors have separate mechanisms. Likewise some patients had a symptomatic 6 HZ tremor on posture with a second peak at 8-10 HZ in the physiological band. Therefore, the 6 HZ postural tremor is not an exaggeration of physiological tremor. On the basis of wave form and frequency similarities postural tremor, the low frequency type of active or passive cogwheeling, intention tremor and clonus possibly involve a common spinal mechanism. Higher frequency cogwheel phenomenon and action tremor may be an exaggeration of physiological tremor. More than 80% of patients with Parkinson's disease manifest tremors at both 4-5 HZ and 6 HZ. This combination would appear to be the strongest objective criterion for the diagnosis of basal ganglia disease.

Electromyography↗
PubMed1980

Reversed optokinetic nystagmus (OKN): mechanism and clinical significance.

We studied reversed optokinetic nystagmus (OKN) in 31 patients and found that it is actually the patient's own gaze-modulated spontaneous nystagmus shifted to the primary position of gaze by optokinetic stimulation. Two of our 31 patients were known to have congenital nystagmus. Most of the 29 others were adults who presented with neurological symptoms and nystagmus and were therefore suspected of having posterior fossa lesions. However, their nystagmographic findings and benign natural history suggest that they also had congenital nystagmus, which was unrecognized until they developed incidental neurological symptoms. These cases support the view that reversed OKN is pathognomonic of a benign, probably congenital, nystagmus.

Adult↗
PubMed1980

Treatment of periodic alternating nystagmus.

Two patients with longstanding acquired periodic alternating nystagmus (PAN) were treated with baclofen, 30 mg/day. Baclofen abolished the PAN and relieved oscillopsia in both patients but was ineffective in another patient with congenital PAN.

Adult↗
PubMed1979

Acute glomerulonephritis in an adult with infected ventriculoatrial shunt.

A case of acute glomerulonephritis occurring during Staphylococcus albus infection of a ventriculoatrial shunt is described. It is the first case in which renal biopsy was repeated after clinical cure by shunt removal. This indicates that isolated haematuria and some histopathological changes may persist for at least a year.

Acute Disease↗
PubMed1979

Ocular tilt reaction with peripheral vestibular lesion.

Following inadvertent destruction of the left vestibular labyrinth during stapedectomy, a patient developed a transient abnormality of posture consisting of leftward ocular counterrolling, leftward had tilting, and a right-over-left skew deviation. This postural pattern, known as the "ocular tilt reaction," is the normal compensatory response of the dependent utricle to tilting. In this patient, the unopposed action of the intact right utricle was presumably responsible for the appearance of a normal leftward ocular tilt reaction.

Adult↗
PubMed1979

Clinical signs of visual-vestibular interaction.

Visual suppression of vestibulo-ocular reflexes (induced vestibular nystagmus) differs between normal subjects and patients with various neurological disorders. Abnormalities of VOR suppression were associated consistently with abnormalities of the visual and/or vesitibular oculomotor reflexes and in particular with abnormal smooth pursuit eye movements in the direction of abnormal suppression. Absent VOR suppression in a gaze position of, and in the same direction as, a spontaneous nystagmus was found exclusively in patients with spontaneous nystagmus of central nervous system origin. Conversely, ability to suppress in these circumstances was found only in patients with spontaneous nystagmus of peripheral labyrinthine origin. Suppression of VOR was abnormal ipsilaterally in patients with unilateral cerebral hemisphere lesions and abnormal in both the horizontal and vertical planes in patients with basal ganglia lesions. Failure of VOR suppression in the absence of spontaneous nystagmus indicates a supratentorial lesion.

Adult↗