Transient cortical blindness due to hypertensive encephalopathy. Magnetic resonance imaging correlation.

Striking reversible signal intense magnetic resonance imaging (MRI) lesions were observed in the occipital cortex of a 16-year-old girl who presented with an attack of transient cortical blindness as the initial manifestation of hypertensive encephalopathy (HTE). The lesions were seen to best advantage on T2-weighted imaging and were not visible on computed tomography (CT). It is proposed that such occipital lobe MRI lesions likely reflect extravasation of fluid and proteins across the blood brain barrier, damaged as a consequence of cerebral autoregulation failure.

The clinical significance of the bifid or "W" pattern reversal visual evoked potential.

Although the visual evoked potential (VEP) to an alternating checkerboard stimulus is usually recorded from the occipital midline as an N-P-N complex with a major positive deflection at 100 ms (P100), a wave form exhibiting a P-N-P or "W" morphology is occasionally encountered and its interpretation is the source of some controversy. A retrospective chart review identified 15 patients exhibiting the "W" VEP. This represented 7.6 percent of 197 VEP studies and 5.1 percent of 394 eyes. The response was encountered in 1.7 percent of 57 normal patients and 21.4 percent of 56 patients with definite, probable or possible multiple sclerosis (P less than .001). The "W" response was considered normal in only one patient. Of the remaining 14 cases, 13 had definite, probable or possible MS and one had ischemic optic neuropathy. It is concluded that the "W" VEP is an aberrant response that is rarely seen in normals and may have the same significance as a delayed P100 latency.

Subjective oscillopsia ("jiggling" vision) presumably due to aminoglycoside ototoxicity. A report of two cases.

Following aminoglycoside antibiotic therapy, two patients developed self-limited subjective oscillopsia in the absence of a detectable ocular motility disturbance (nystagmus or opsoclonus). Oscillopsia represents a rare, but highly distressing symptom resulting from disruption of the vestibulo-ocular reflex, producing profound illusory movement of the visual environment. Although the differential diagnosis includes vascular, inflammatory, and structural disorders impacting on either the central or peripheral projections of this brainstem reflex, iatrogenic aminoglycoside ototoxicity was the likely explanation in the two patients presented. Ways of minimizing the risk of aminoglycoside toxicity are briefly reviewed.

Multiple sclerosis with onset after age 60.

The onset of multiple sclerosis (MS) after age 60 is uncommon. The clinical features of three such cases are described. Considerable diagnostic delay was seen in each case as symptoms were initially attributed to other conditions that more commonly afflict the elderly, including atypical facial pain, neuropathy, peripheral and cerebral vascular disease, arthritis, benign prostatic hypertrophy, and ischemic optic neuropathy. Although MS should be considered a diagnosis of exclusion in this age group, cerebral evoked potentials and CSF immunoglobulin studies can increase the diagnostic yield and may be helpful in the appropriate clinical context.

Hemiparesis apparently due to central pontine myelinolysis following hyponatremia.

A 63-year-old woman was in an acute confusional state accompanied by rapidly progressive left hemiparesis, dysphagia, and dysarthria two weeks after an episode of diuretic-induced hyponatremia. High-resolution computed tomographic scanning disclosed a circumferential hypodense pontine lesion compatible with the diagnosis of central pontine myelinolysis. Although the patient improved clinically within six weeks, the computed tomographic abnormalities remained unchanged.

The origins of the subcortical component of the median nerve somatosensory evoked potentials.

Short latency median nerve somatosensory evoked potentials (SEPs) were studied in two patients presenting with well localized unilateral pontine lesions producing hemisensory deficits. Both the early subcortical (N11-N13) and the later cortical component (N19-P22) of the SEP were abnormal in the patient whose lesion involved the medial lemniscus, while they remained unaffected in a second case of lateral inferior pontine infarction in which the medial lemniscus was spread. These results suggest that the N11-N13 component of the scalp recorded SEP emanates from the brain stem medial lemniscal pathway.

Tourette syndrome, an acquired encephalopathy? A report of two cases with epileptiform dysrhythmia.

The electroencephalogram, although providing no specific diagnostic information for Tourette syndrome, may be useful in evaluating the pathology in which the syndrome occurs, since it appears that at least some cases may occur in the setting of an underlying acquired encephalopathy of diverse etiology. A neurochemical basis for the Tourette syndrome expressed as an extrapyramidal circuit imbalance may also relate to a discharge threshold for epileptiform activity. A more detailed electroencephalographic evaluation of such patients using nasopharyngeal or sphenoidal recording may be useful in this regard.

Supraclavicular and carotid bruits in hemodialysis patients.

Auscultation of the neck vessels in patients receiving chronic hemodialysis reveals a high incidence of subclavian and carotid bruits as well as the expected precordial hemic murmurs. These bruits are associated with the high-output hyperdynamic circulatory state. In older patients the finding could be misinterpreted as evidence of extracranial cerebrovascular disease, but clinical considerations should obviate unnecessary neuroradiological diagnostic procedures.