MRI findings in Susac's syndrome.

BACKGROUND: Susac syndrome (SS) is a self-limited syndrome, presumably autoimmune, consisting of a clinical triad of encephalopathy, branch retinal artery occlusions, and hearing loss. All three elements of the triad may not be present or recognized, and MR imaging is often necessary to establish the diagnosis. OBJECTIVE: To determine the spectrum of abnormalities on MRI in SS. METHODS: The authors reviewed the MR images of 27 previously unreported patients with the clinical SS triad, and 51 patients from published articles in which the MR images were depicted or reported. RESULTS: All 27 patients had multifocal supratentorial white matter lesions including the corpus callosum. The deep gray nuclei (basal ganglia and thalamus) were involved in 19 (70%). Nineteen (70%) also had parenchymal enhancement and 9 (33%) had leptomeningeal enhancement. Of the 51 cases from the literature, at least 32 had callosal lesions. The authors could not determine the presence of callosal lesions in 18 of these patients, and only one was reported to have a normal MRI at the onset of encephalopathy. CONCLUSIONS: The MR scans in SS show a rather distinctive pattern of supratentorial white matter lesions that always involve the corpus callosum. There is often deep gray matter, posterior fossa involvement, and frequent parenchymal with occasional leptomeningeal enhancement. The central callosal lesions differ from those in demyelinating disease, and should support the diagnosis of SS in patients with at least two of the three features of the clinical triad.

Random comments: neurologists and neuro-ophthalmology; the "ocular motor" system; and update on ophthalmoplegic migraine.

In this brief commentary, I recount the entry of neurologists into the field of neuro-ophthalmology, which was previously regarded as exclusively within the purview of ophthalmology. I then quickly describe the difference between "oculomotor" and "ocular motor," before summarizing "ophthalmoplegic migraine," a rare condition with a rich history that engendered a heated debate among legendary neurological luminaries in 1946.

Neurology in a combat zone: Viet Nam 1966.

I summarize my experience as the first neurologist serving the US Forces in Viet Nam, 24 December, 1965 to 18 November, 1966. Stationed at the 93rd Evacuation Hospital in Long Binh, and working with a KO (neuro-psychiatric) team, I saw a wide variety of patients under conditions unique for a neurologist.

Whipple's disease mimicking progressive supranuclear palsy: the diagnostic value of eye movement recording.

Treatable causes of parkinsonian syndromes are rare; Whipple's disease is one of them. A patient is described who presented with a parkinsonian syndrome and abnormal vertical gaze. Measurement of eye movements showed marked slowing of upward saccades, moderate slowing of downward saccades, a full range of voluntary vertical eye movements, curved trajectories of oblique saccades, and absence of square wave jerks. These features, atypical of progressive supranuclear palsy, suggested the diagnosis of Whipple's disease, which was subsequently confirmed by polymerase chain reaction analysis of intestinal biopsy material. Precise measurement of the dynamic properties of saccadic eye movements in parkinsonian patients may provide a means of identifying treatable disorders.

Two additional scenarios for see-saw nystagmus: achiasma and hemichiasma.

The discovery of canine achiasma and hemichiasma has been followed by the identification of human achiasma (four individuals, to date). See-saw nystagmus was present in all cases of achiasma (canine and human) and in one of two cases of canine hemichiasma studied. Human infants with see-saw nystagmus should be imaged for possible structural abnormalities of the optic chiasm.

Acute intermittent porphyria: clinicopathologic correlation. Report of a case and review of the literature.

Acute intermittent porphyria (AIP), an autosomal dominant disorder, results from a deficiency of the enzyme hydroxymethylbilane synthase. Despite important advances in the characterization of AIP, the pathophysiology of the neurologic manifestations is not clearly understood. We present a patient with AIP followed for 31 years with multiple episodes of hyponatremia during AIP exacerbations. We discuss the clinicopathologic correlation and possible explanations for the morphologic findings, including discrete hypothalamic changes.

Two types of foveation strategy in 'latent' nystagmus: fixation, visual acuity and stability.

The authors studied the foveation dynamics of two individuals with latent/manifest latent nystagmus (LMLN) to test the hypothesis that oscillopsia suppression and good visual acuity require periods of accurate target foveation at low slip velocities. Congenital nystagmus (CN) waveforms contain post-saccadic foveation periods; the LMLN waveform does not and yet allows for both oscillopsia suppression and good acuity. During fixation with both eyes open, there were intervals when the eyes were still and correctly aligned; at other times, there was esotropia and nystagmus with slow-phase velocities less than +/- 4 deg/sec and each fast phase pointed the fovea of the fixating eye at the target. However, cover of either eye produced LN and a different strategy was employed: the fast phases carried the fixating eye past the target and the fovea subsequently reacquired it during the slowest parts of the slow phases. The authors confirmed this in both subjects, whose high acuities were made possible by foveation occuring during the low-velocity portions of their slow phases. A nystagmus foveation function (NFF), originally developed for CN, was calculated for both LN and MLN intervals of fixation and it was found to track visual acuity less accurately for individuals with high acuity. Individuals with LMLN exhibit two different foveation strategies: during low-amplitude LMLN, the target is foveated immediately after the fast phases; and during high-amplitude LMLN, target foveation occurs towards the end of the slow phases. Therefore, the saccadic system can be used to create retinal error rather than eliminate it if this strategy is beneficial. Individuals with LMLN foveated targets with the same eye-position and -velocity accuracy as those with CN and the NFF provides a rough estimate of acuity in both. Current calibration methods for both infrared and search-coil techniques need to be altered for subjects with LMLN.

Postmortem examination of relapsing acute Guillain-Barre syndrome.

We report a patient who had six episodes of acute Guillain-Barre syndrome during his life. He is the fifth such case with postmortem analysis.