Unusual effects of metrizamide lumbar myelography. Constellation of aseptic meningitis, arachnoiditis, communicating hydrocephalus, and Guillaine-Barré syndrome.

A clinical constellation of aseptic meningitis, arachnoiditis, communicating hydrocephalus, and a Guillain-Barré syndrome occurred following lumbar myelography with metrizamide. To our knowledge, Guillain-Barré syndrome has not been previously described following myelography with any contrast agent. Meningeal reactions and hydrocephalus have been reported with other agents, but this is the first instance with metrizamide.

Macro square wave jerks.

Quantitative eye movement recordings in a patient with multiple sclerosis who had both macro square wave jerks and an internuclear ophthalmoparesis supported the concept of an internal brain-stem monitor that mediates corrective eye movements. A brain-stem model of this monitor illustrates the patient's motility disorder and the normal function of providing synergistic version and vergence corrections for dysmetric eye movements. Thus, the careful study of pathologic disturbances provides information relevant to the normal operation of the ocular motor system.

Edrophonium infrared optokinetic nystagmography in the diagnosis of myasthenia gravis.

Horizontal optokinetic nystagmus was measured by an infrared eye movement recording technique before and after the administration of intravenous edrophonium chloride in 16 patients wtih proved myasthenia gravis. All the patients, even those without clinically apparent ophthalmoparesis, demonstrated an increased amplitude of optokinetic nystagmus after administration of the drug. None of 12 control patients, many with ophthalmoparesis, showed increased optokinetic nystagmographic amplitude. The superiority of infrared recording techniques to electro-ocuography was discussed. Edrophonium infrared optokinetic nystagmography proved to be a sensitive and specific test of myasthenic weakness in extraocular muscles.

Edrophonium test in Eaton-Lambert syndrome: quantitative oculography.

Accurate ocular motility recordings were made of the saccadic responses of five patients with Eaton-Lambert syndrome (ELS). It was found that, contrary to common belief, the ocular motor system is affected. The saccades of ELS patients mimicked those of patients with myasthenia gravis (MG). Both groups exhibited hypometria and multiple, closely spaced saccades. Two patients demonstrated both saccadic facilitation and positive edrophonium tests. The ELS patients had slow or normal saccadic velocities, not the "super-fast" velocities found in patients with ocular MG.

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.

Latent/manifest latent nystagmus reversal using an ocular prosthesis. Implications for vision and ocular dominance.

Latent/manifest latent nystagmus (LMLN) is a jerk nystagmus with a decreasing-velocity or linear slow phase whose fast phase is in the direction of the fixating eye. Change of the fixating eye by alternating tropias or cover will cause reversal of the LMLN to preserve this relationship. In the dark, where no fixation is possible, the fast phases of LMLN are in the direction of the intended fixating eye; actual visual input will override this effect of intention. A patient with persistent hyperplastic primary vitreous of the right eye, which was enucleated at age 9 due to glaucoma, had LMLN with fast phases to the left. His congenitally blind right eye was replaced with an ocular prosthesis whose movements were conjugate with his seeing eye. In the dark, we found that his LMLN spontaneously reversed as the normally fixating left eye became esotropic. Furthermore, as is the case with LMLN patients who have sight in both eyes, he was able to willfully reverse his LMLN in the dark by alternating his "fixating" eye. We conclude from these observations that the direction of LMLN is determined at a cortical level, is intimately related to the intended fixating eye and that eye "dominance" is predetermined and not altered by visual abnormalities, including blindness.

Saccades in extremes of lateral gaze.

Saccades (between targets at 30 degrees and 40 degrees) were recorded with DC electro-oculography in 10 normal subjects. Velocity-amplitude relationships were examined on the basis of abduction vs. adduction and centering vs. eccentric movement. In these small peripheral saccades the former pairing showed no consistent differences in peak velocity, whereas centering saccades were consistently faster than both eccentric movements and those made around primary position.

Internuclear ophthalmoplegia: recovery and plasticity.

We studied refixational eye movements of a patient during the gradual resolution of an internuclear ophthalmoplegia (secondary to head trauma) in an attempt to determine the relative contributions of both medial longitudinal fasciculus (MLF) recovery and secondary central plastic changes. Adduction-refixational eye movements in the affected eye consisted of an initial fast (saccadic) portion followed by a slow drift toward the new intended eye position. The fast and slow components of the movements reflected, respectively, the pulse and step increases in neural innervation. Shortly after the traumatic insult, the affected eye exhibited low adduction gain (pulse gain 0.34; step gain 0.37) and slow saccades with peak velocities of 55% and durations of 278%, normalized for achieved, rather than intended, amplitudes. Several months later the pulse and step gains, peak velocities, and durations of the saccades improved to 0.81, 0.92, 87%, and 145%, respectively. The increased gains and faster velocity were accomplished by increases in the firing frequency of the pulse and step, reflecting recovery of MLF axons, rather than saccadic system plasticity, which would have resulted in increased duration of the saccadic pulse.

End-point nystagmus.

Infrared oculography was performed during sustained lateral gaze in 12 normal subjects to investigate end-point nystagmus while fixating a target light. Five failed to develop nystagmus despite deviation up to 40 degrees from 4 to 5 min. Six subjects developed nystagmus immediately or shortly after reaching the deviated position. In one, the nystagmus (0.5 degrees to 1 degree and 1.0 Hz) began with only a 20 degree deviation. In another subject, "fatigue" nystagmus developed after 1 min at 30 degrees, and at 35 degrees nystagmus began within 2 sec. One subject developed only fatigue nystagmus, which began after more than 4 min of sustained deviation. In all instances the slow phase had primarily a linear, rather than exponential, waveform.

Latent, manifest latent, and congenital nystagmus.

Manifest latent nystagmus (MLN) was identified in 31 patients by accurate eye movement records. All the patients had horizontal tropias, and the nystagmus fast phases were always in the direction of viewing eye. The slow phases of MLN are decreasing-velocity exponentials while those of the jerk form of congenital nystagmus (CN) are increasing velocity exponentials. Several subjects who were believed to have latent nystagmus (LN) on clinical examination had small amplitude nystagmus evident by eye movement recording with both eyes open: these were actually cases of MLN. Many patients with MLN are misdiagnosed as having CN. An explanation for MLN and LN is provided based on confusion of egocentric directions between monocular and binocular viewing conditions.

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.

Television-induced formed visual hallucinations and cerebral diplopia.

A 65-year-old man with ischaemic encephalomalacia following surgery for an aortic arch aneurysm experienced episodes of stereotyped formed visual hallucinations uniquely provoked by television viewing. In addition he noted vertical diplopia of cerebral origin. These symptoms are discussed in the light of what is known about visual hallucinations, television-induced epilepsy, and cerebral polyopia.

Ocular oscillations.

A variety of abnormal ocular oscillations consequent to brain stem and cerebellar dysfunction are described. The brain stem eye signs include: see-saw nystagmus, convergence-retraction nystagmus, down-beat nystagmus, ocular myoclonus, ocular bobbing, and superior oblique myokymia. The "cerebellar system" eye signs discussed are five varieties of nystagmus, square wave and macro square wave jerks, macro saccadic oscillations, ocular dysmetria and flutter, and opsoclonus.

Alexander's law: a model and resulting study.

Recently we developed an analog model to simulate Alexander's law in nystagmus secondary to dysfunction of a semicircular canal. Alexander's law is based on the observation that the amplitude of the nystagmus grows with increasing gaze in the direction of the fast phase and diminishes with gaze in the opposite direction. To investigate the assumptions made in the model, we conducted quantitative experimental studies on the effect of gaze on caloric-induced nystagmus in human subjects. A weak stimulus (water at 26.5 degrees C and 240 ml/min) was administered for several minutes which caused the development of jerk nystagmus. Both the average slow phase velocity and frequency reached a steady state at about three minutes after the start of irrigation and remained stable until the flow of water was stopped. To investigate the effect of gaze, each subject was asked to hold gaze at various positions from center, to the right, to the left, and to repeat the cycle. Results indicated that the slow phase velocity of the nystagmus was greatest in the direction of the fast phase and decreased approximately linearly with gaze in the other direction in accordance with Alexander's law. Frequency was not a function of gaze. We speculate as to the biological advantages of the brainstem neural circuitry responsible for Alexander's law.

Space motion sickness: etiological hypotheses and a proposal for diagnostic clinical examination.

The general notion that space motion sickness (SMS) is due to a "conflict" between vestibular, visual, and other sensory inputs has gained popular acceptance. We have reviewed three specific hypotheses for SMS and identified characteristic disorders of ocular motility that each hypothesis would predict. Accurate recording of horizontal and vertical eye movements during free head movements in space craft presents technical difficulties. We suggest that careful clinical examination may be useful, provided the examination is directed towards detecting those specific abnormalities predicted by each hypothesis.

Braking saccade--a new fast eye movement.

A new type of fast eye movement (FEM) is described whose main function is to stop a runaway slow eye movement (SEM). It conforms to the velocity-amplitude relationship characteristic of other types of saccades. The identification of this FEM is the result of examination of the many waveforms manifested by subjects with congenital nystagmus. It is a common, repeatable phenomenon present in all subjects with any of six different types of nystagmus waveform. The fact that braking saccades reset SEM to zero velocity, whereas no other type of saccade interacts with SEM, indicates a developmental mechanism in such subjects.

Saccadic velocity characteristics: intrinsic variability and fatigue.

Saccadic eye movements exhibit a characteristic peak velocity vs. amplitude relationship. As with all quantifications of biological function, there exists and associated intra- and intersubject variability of this relationship. This paper documents this variability and demonstrates both the absence of a predictable short-term "muscle fatigue" effect and the presence of a generalized "mental fatigue" (i.e. tiredness) effect.

An approach to migraine.

Since headache is one of the most common symptoms experienced in the general population, the neuroscience nurse should understand the phenomenon of migraine. We define the various types of migraine and present a strategy, based upon precipitators, inhibitors and a "migraine threshold" to facilitate patient education.

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.