Downbeat nystagmus with magnesium depletion.

Two patients with neurological signs of magnesium depletion complained of oscillopsia and manifested downbeat nystagmus. Serum magnesium levels measured less than 1.0 mg/dL. Hypomagnesemia resulted from debilitating intestinal disease in both patients and apparently was aggravated in one case by failure to add magnesium sulfate to the patient's regimen for total parenteral nutrition. Neither patient had any of the neurological conditions reported with downbeat nystagmus. Thus, downbeat nystagmus in the primary position occurs with the metabolic derangement of severe magnesium depletion. Another apparent metabolic cause of downbeat nystagmus is thiamine deficiency. Downbeat nystagmus also may occur from a partial deficiency of the metabolic cofactors, magnesium and thiamine.

Superior oblique myokymia: quantitative description of the eye movement.

We studied superior oblique myokymia (intermittent uniocular microtremor) using magnetic scleral search coils. The monocular disorder consisted of both phasic and tonic components consistent with the primary, secondary, and tertiary actions of the superior oblique muscle. These observations support the hypothesis of a disorder restricted to the superior oblique motor unit.

Diffusely infiltrating brainstem gliomas: a report of the diagnostic difficulties in 2 cases.

Brainstem gliomas seem to present in 2 distinct ways. More commonly they are localized to 1 portion of the brainstem and present with signs that are both localizing and lateralizing. These are usually fairly easy to image neuroradiologically. The rarer diffusely infiltrating variety manifest a slowly building array of findings pointing to all levels and both sides of the brainstem. Our 2 cases exemplify the diffuse variety. They were clinically typical, and the CSF pressure and protein were elevated but the neuroimaging abnormalities were so subtle that they were originally overlooked. This subtlety of neuroradiologic abnormality resembles that found in gliomatosis cerebri.

Dissecting aneurysms of head and neck.

We analyzed four personal cases and 51 reported cases of dissecting aneurysms of the arteries of the head and neck. Subintimal dissection more commonly affects the intracranial vessels before age 40. In contrast, medial dissection tends to affect extracranial vessels after age 30. Vertebrobasilar dissection more variably affects either arterial plane. The reasons for these differing patterns of dissection are still not clear. In young subjects, the subintimal layer appears to be more susceptible; in contrast, the media becomes increasingly vulnerable with age, particularly in the presence of acquired medial disease.

Ocular neuromyotonia. A clinical description of six patients.

We report the cases of six patients with ocular neuromyotonia, a disorder believed to result from episodic involuntary discharge of ocular motor nerves producing sustained and inappropriate contraction of their respective ocular muscles. Transient disturbances of ocular motility and diplopia result. Four patients had involvement of ocular muscles supplied by the third cranial nerve: one had presumed involvement of the superior oblique muscle, and one the lateral rectus muscle, suggesting abnormal discharge in the fourth and sixth cranial nerves, respectively. Four of six patients received prior radiation therapy for pituitary tumors, implying a possible pathogenic link. Three patients improved after treatment with membrane-stabilizing medication, suggesting that unstable membranes of injured ocular motor axons may generate spontaneous impulses, which produce involuntary sustained and inappropriate ocular muscle contraction.

Emergency diagnosis of pituitary apoplexy.

A 60-year-old man, chronically anticoagulated for a prosthetic heart valve, suffered visual loss from hemorrhage into an unsuspected pituitary tumor. The diagnosis of pituitary apoplexy was made in the emergency department. The patient's coagulopathy was reversed, and he underwent an uneventful transsphenoidal hypophysectomy. Marked recovery of vision occurred over the next six months. The clinical features of this uncommonly diagnosed syndrome are reviewed, and the importance of recognizing this entity with the advent of computed tomographic scanning is emphasized.

Uhthoff and his symptom.

At the turn of the last century, Wilhelm Uhthoff was a renowned clinical neuro-ophthalmologist, and probably the first clinician whose entire career was devoted to this discipline. His achievements are among those that mark the commencement of contemporary neuro-ophthalmology. Uhthoff's symptom of visual loss with exercise is most frequently associated with optic neuritis. The symptom carries a major risk for recurrence of optic neuritis and development of multiple sclerosis. This study and its companion in the publication show that, independently, a metabolic byproduct of exercise or increases in body temperature cause a reversible conduction block in demyelinated optic nerves and result in temporary loss of vision [corrected].

Transient visual loss after licorice ingestion.

The authors present a spectrum of clinical presentations of transient visual loss/aberrations and show that these occurrences were attributable to ingestion of significant amounts of licorice. A case series of five patients was seen at Geisinger Medical Center between October 1986 and May 1996. Details of patient presentation, treatment, and outcome are discussed. The literature on the effects of licorice derivatives on vascular smooth muscle function is reviewed. Of the five patients, two had documented visual loss by visual acuity testing and visual fields. All patients reported a recent ingestion of significant amounts of licorice (1/4-2 lbs.). All patients had resolution of their visual symptoms; the aid of hyperbaric oxygen was required for one patient. Thorough review of the literature shows recent in vitro and in vivo evidence of glycyrrhetinic acid (the active component of licorice) and carbenoxolone (the hemisuccinate derivative of glycyrrhetinic acid) directly and indirectly enhancing vasoconstrictor action in vascular smooth muscle. It is believed that licorice derivatives can cause retinal or occipital vasospasm, giving rise to transient monocular or binocular visual loss/aberrations. This has not been described before in the literature. It is important to ask about licorice ingestion with patients who present with these visual symptoms.

Third nerve palsy: the presenting sign of a pituitary adenoma in five patients and the only neurological sign in four patients.

Five male patients sought medical attention for diplopia and were found to have third nerve palsies secondary to pituitary adenomas. In four cases this was the only neurologic abnormality. In the fifth there was an additional, asymptomatic, temporal visual field defect in one eye. Partial third nerve involvement was seen in all but one patient. Four patients underwent successful surgery and were found to have chromophobe adenomas. One patient had clinical and laboratory evidence of Cushing's syndrome. An initial diagnosis of cerebral aneurysm was made in three cases when the third nerve palsy followed a severe, acute headache. Later it became evident that pituitary apoplexy was the correct diagnosis. The mechanisms by which a pituitary adenoma causes a third nerve palsy are discussed. The importance of recognizing a pituitary tumor as the etiology of an isolated third nerve palsy is emphasized.

Spontaneous reduction of growth rate of a large intracranial meningioma. Case report.

A relatively young patient with a large intracranial meningioma producing a paucity of neurological signs and symptoms showed no progression of symptomatology over 14 years. This may represent a spontaneous growth arrest in an otherwise early expected fatal outcome. The location of the tumor with its benign course producing no demonstrable increase in visual loss over 14 years in such a young patient is quite unusual.

Sudden hemiparesis as the presenting sign in cryptococcal meningoencephalitis.

A previously healthy young man presented with an acute stroke syndrome and was found to have cryptococcal organisms in the CSF. Though an initial CSF examination for an infectious etiology was negative, a second lumbar puncture was performed because of hypoglycorrhachia, which established the diagnosis. An uneventful recovery followed the administration of Amphotericin B and 5-Flucytosine. A literature search revealed only one previously reported case of cryptococcal meningoencephalitis presenting as a stroke. The need for performing a CSF examination on young patients presenting with a cerebrovascular event, and the aggressive investigation of unexplained hypoglycorrhachia are emphasized.

Visual evoked potentials during hyperthermia.

OBJECTIVES: We sought to evaluate the effect of hyperthermia (HT) on central conduction pathways by alterations in pattern visual evoked potentials (PVEPs) in normal and demyelinated optic nerves. MATERIALS AND METHODS: We studied PVEP peak latency and amplitudes in 10 normal subjects and six patients with demyelinating optic neuropathy before and during HT. RESULTS: In normal subjects, a mean rise in temperature of 2.5 degrees C resulted in a decrease in the second positive peak (P2) latency of 6.1 ms (p < 0.0001) and a slight decline in P2 amplitude of 1.16 muV (p < 0.009). These results were compared to those obtained from six patients with multiple sclerosis. These patients had a history of monocular optic neuritis; two patients had had bilateral optic neuritis, and one patient had not had involvement of the optic nerve. Average temperature elevations during PVEPs were 1.60 degrees C. PVEPs among these patients showed decrease in mean P2 latencies, except in patients with multiple sclerosis, who showed an increase in latency with 60 min check size in the left eyes. There was a consistent decline in P2 amplitudes. Loss of amplitude was greater among the six optic nerves of those patients having transient, mild losses in visual acuity during HT. Reductions in P2 amplitude were best explained by partial or complete conduction block. CONCLUSIONS: These changes in conduction time and amplitude during HT provide a neurophysiologic correlation to the well-known sensitivity of demyelinated optic nerves to elevated temperatures. They are also relevant to the monitoring of central pathways in the operative or intensive care setting. The demonstrated reversible loss of amplitudes also gives promise to therapeutic manipulation of impaired pathways by impeding the loss of current from denuded nerve fibers.

Pseudotumor cerebri secondary to lithium carbonate.

Three patients were initially seen with headache, blurred vision, and papilledema while taking lithium carbonate for their respective bipolar affective disorder. A diagnosis of pseudotumor cerebri was made in each case when a thorough evaluation revealed only elevated intracranial pressure. Two of the patients had complete resolution of their symptoms and papilledema after discontinuing use of the drug. Increased intracranial pressure with papilledema persisted in the third patient when she failed to adjust psychiatrically, necessitating continuance of the lithium carbonate therapy. A history of lithium carbonate ingestion should be sought in patients with the syndrome of pseudotumor cerebri. All patients receiving this drug should have a regular funduscopic examination.

Cerebral infarction in young adults.

The etiologic and prognostic features which characterize cerebrovascular disease in the later decades of life are not applicable in younger patients. The records of 58 patients who had suffered cerebral infarction between the ages of 15 and 40 were reviewed in order to study these features. Fifty-five percent of the patients were found to have had an identifiable etiology for their cerebral infarction, with nearly half of these suffering from embolic infarction of cardiac origin. In 45% no clear etiology could be established but hypertension was prevalent in those patients between 31 and 40 years of age. Follow up data were obtained on 68% of the hospital survivors; nearly 3/4 of them had completely recovered or had improved.

Severe dysthyroid orbitopathy.

Nineteen patients (12 women and 7 men) with severe dysthyroid orbitopathy were treated with either orbital irradiation (9 patients) or orbital decompression (10 patients) or both (1 patient). Eight of the nine patients who received orbital irradiation had a favorable response. One patient had progression of optic neuropathy despite orbital irradiation and required orbital decompression. All eleven patients who underwent orbital decompression had a favorable response.

Meso-diencephalic infarction: a not so rare form of stroke.

26 patients admitted with clinical pictures consistent with meso-diencephalic infarction were studied using computerized axial tomography, magnetic resonance imaging and angiography. All of the patients presented symptoms in two of three major categories which comprise the "top of the basilar" syndrome. Lesions in the territory of the basilar-communicating artery were demonstrated in 22 of them. The remaining patients died before adequate neuroimaging documentation was obtained. Overall prognosis appeared relatively good since 80% of the patients recovered completely or incompletely from the ictus. Meso-diencephalic infarction is a very important and not uncommon subtype of cerebrovascular disorder.