Robert B. Daroff

The International Classification of Sleep Disorders: Diagnostic and Coding Manual

I congratulate the American Sleep Disorders Association for this outstanding manual, modeled after DSM-111 and consistent in style with the ICD-9-CM Classification. Like the DSM-111, it is more than an outline; it includes diagnostic criteria, clinical course, predisposing factors, prevalence, differential diagnosis, and a bibliography for each of the numerous disorders. The book obviously is essential for polysomnographers, but all neurologists seeing patients with sleep disorders or sleep-related phenomena should have i t available.

Review of the toxicology of chlorpyrifos with an emphasis on human exposure and neurodevelopment

This review examines the large body of toxicological and epidemiological information on human exposures to chlorpyrifos, with an emphasis on the controversial potential for chlorpyrifos to induce neurodevelopmental effects at low doses. The results of this review demonstrate that the use of urinary 3,5,6-trichlorpyridinol (TCPy), a metabolite of chlorpyrifos as a biomarker of nonoccupational exposure is problematic and may overestimate nonoccupational exposures to chlorpyrifos by 10-to 20-fold because of the widespread presence of both TCPy and chlorpyrifos-methyl in the food supply. Current “background” (nonoccupational) levels of exposure to chlorpyrifos are several orders of magnitude lower than those required to inhibit plasma cholinesterase activity, which is a more sensitive target than nervous system cholinesterase. However, several in vitro studies have identified putative neurodevelopmental mechanisms that are altered at concentrations of chlorpyrifos below those that inhibit cholinesterases. Although one human cohort study reported an association between maternal and cord blood chlorpyrifos levels and several measures of neurodevelopment, two other cohort studies that utilized urinary TCPy as a surrogate for chlorpyrifos exposure did not demonstrate an association. Although the weight of the scientific evidence demonstrates that current levels of chlorpyrifos exposure will not have any adverse effects on neurodevelopment that might result from inhibition of nervous system cholinesterases, several recent studies propose alternative mechanisms. Thus, further in vivo investigation on neurodevelopment in an appropriate animal model is needed; additional epidemiological studies may be warranted if a suitable, chlorpyrifos-exposed cohort can be identified and more rigorous measures of exposure are utilized.

Congenital nystagmus waveforms and foveation strategy

Accurate eye movement recordings of sixty-five subjects with congenital nystagmus (CN) provides a firm foundation for the classification of the many types of wave-forms observed and results in objective definitions based on measurable quantities rather than subjective clinical impressions. The careful scrutiny of these records along with the utilization of laser-target retinal cinematography have yielded insights into the mechanism of this ocular motor instability.Prolongation of target foveation emerges as the dominant factor in many of the resultant waveforms. This enhances the visual acuity of the subject with CN. An additional observation, related to fixation bias reversals of the CN subject, may be a physiological indicator of foveal function.

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.

Therapy for benign paroxysmal positioning vertigo, revisited.

Benign paroxysmal positioning vertigo (BPPV) is a mechanical disorder of the inner ear in which precipitating positioning of the head causes an abnormal stimulation, usually of the posterior semicircular canal of the undermost ear. Schuknecht1j2 hypothesized that heavy debris settles on the cupula (“cupulolithiasis”) of the canal, transforming it from a transducer of angular acceleration into a transducer of linear acceleration. There is now general acceptance that the debris floats freely within the endolymph of the canal (“~analoli thiasis”).~-~ The debris, consisting of particles possibly detached from the otolith, congeals to form a freefloating clot (plug); since the clot is heavier than the endolymph, it will always gravitate to the most dependent part of the canal during head position changes that alter the angle of the cupular plane relative to gravity. Analogous to a plunger, the clot induces bidirectional (push or pull) forces on the cupula, thereby triggering the BPPV attack. Canalolithiasis explains all the features of BPPV: latency, short duration, fatigability (diminution with repeated positioning), changes in direction of nystagmus with changes in head position, and the efficacy of physical the rap^.^,^

Corrective movements following refixation saccades: Type and control system analysis

Abstract Refixational saccades frequently do not achieve the intended amplitude with the initial displacement; the errors are either equal in the two eyes (conjugate) or dysconjugate. A binocular saccadic (high-velocity) corrective movement (CM) follows conjugate dysmetria after a 125 msec latency. Slow, drift-tike glirsadic CMs, continuous with the termination of the original saccade, correct dysconjugate errors. We discuss the possible rotes of “pre-packaging” and visual, proprioceptive and internal prenuclear feedback in the generation of CMs. We conclude that a prenuclear internal monitor best accounts for glissadic CMs whereas saccadic CMs may be explained by either proprioceptive feedback or an internal monitor.

A new look and feel Message from the Editor-in-Chief

Neurology, the official journal of the American Academy of Neurology, began in 1951 with founding editor Russell N. DeJong. A.B. Baker, then President of the Academy, had enticed his publisher friend Louis M. Cohen in Minneapolis (who owned Modern Medicine, a subsidiary of Lancet Publications) to publish the journal. During the last 45 years, mergers, acquisitions, and bankruptcies have changed the name of the publisher several times: Lancet Publications became a subsidiary of Cowles Communications in 1970, and two years later, a subsidiary of the New York Times Media Company, which in turn became a subsidiary of Harcourt Brace Jovanovich (HBJ) in 1977, and later, Edgell Communications, then Advanstar Communications. The production quality of the journal, however, never suffered. Despite the ownership changes, Staff Editor Peter …

The metrics of horizontal saccadic eye movements in normal humans

Abstract The metric characteristics of horizontal saccadic eye movements are defined and analyzed following detailed electro-oculographic recordings in 25 normal subjects. Small (10°) saccades are usually normometric, but accuracy decreases with larger amplitudes producing undershoots of the fixation targets. Approximately 20 per cent of 20° and 30° saccades are transiently dysconjugate (1°–3°) at termination. The most common dysconjugate pattern demonstrates excessive convergence due to momentary overshooting of the adducting eye or undershooting of the abducting eye. The authors question an inviolate interpretation of Herings Law and discuss the mechanisms of the dysconjugacies in light of current concepts of the neurophysiology of eye movements.

Pathology of oculomotor nerve palsy in diabetics

SUMMARYThe pathological findings of pupil-sparing oculomotor palsy in a diabetic patient are presented and discussed in view of the 2 other published necropsy studies of this disorder. Intraneural arteriolar abnormalities were seen in all 3, but our patient was the first in whom the pathological neural process involved the subarachnoid segment of the third nerve.

SEE-SAW NYSTAGMUS.

SEE-SAW NYSTAGMUS is a n unusual bu t distinctive phenomenon initially described by Maddox in 1914.l Just twelve additional cases have been reported subsequently.”-lO The characteristic feature of the nystagmus is that one eye rises while the other eye falls, resembling the action of a see-saw. Actually, as originally noted by Maddox,l and in most other cases in which it is carefully described, the nystagmus is basically rotary (torsional) with the eyes moving conjugately clockwise and then counterclockwise. During the torsional movements, the intorting eye elevates while the opposite eye, which is extorting, falls (see figure). Most cases have been reported in association with large parasellar or pituitary tumors which have extended into the third ventricle. One of the two patients to be described had such a lesion. The other probably had cerebrovascular disease involving the brainstem.