A case of Parinaud's syndrome due to the remote effect of small cell carcinoma

Gaze-holding and anti-GAD antibody: prototypic heterogeneous motor dysfunction in immune disease

The variability in motor dysfunction is not uncommon in autoimmune disorders. Antibody-mediated system-wide malfunction or effects on the neural network shared by two independent pathophysiological processes can cause such heterogeneity. We tested this prediction for motor dysfunction during gaze holding in 11 patients with increased titers of glutamic acid decarboxylase (anti-GAD) antibody. High-resolution oculography measured horizontal and vertical eye positions. The analysis was performed with customized signal processing algorithms. Downbeat and gaze-evoked nystagmus commonly coexisted; one patient had a combination of upbeat and gaze-evoked nystagmus. The nystagmus was associated with saccadic intrusions in 10 patients; all had squarewaves, but five also had saccadic oscillations. The nystagmus and saccadic intrusions, both in the same axis of eye rotations, were not uncommon. Tandem appearance of the episodes of nystagmus and saccadic intrusions suggested a coupling between the two abnormalities. We speculated a unifying framework where the anti-GAD antibody inhibited (GAD mediated) conversion of glutamate to gamma-aminobutyric acid (GABA). Paucity GABA and excess of glutamate cause nystagmus (less GABA) and high-frequency saccadic oscillations (excessive glutamate).

Internuclear and supranuclear disorders of eye movements: clinical features and causes

Eye movements bring visual stimuli to the fovea and also maintain foveal fixation on a moving target and during head movements. These movements are performed by the ocular motor system that consists of ocular motor nerves and nuclei in the brainstem originating in the cerebral cortex, cerebellum, vestibular structures, and the extraocular muscles. The ocular motor system is divided according to anatomic location into infranuclear, nuclear, internuclear, and supranuclear components. It is important to distinguish supranuclear and internuclear from nuclear and infranuclear disturbances affecting cranial nerves III, IV, and VI, because the disturbances are of highly varied causes and present different clinical pictures. Internuclear ophthalmoplegia is due to a lesion of the medial longitudinal fasciculus, caused by multiple sclerosis in younger patients, particularly when the ophthalmoplegia is bilateral, and usually of vascular origin in the elderly. Eye movement abnormalities of supranuclear origin are characterized by gaze palsies, tonic gaze deviation, saccadic and smooth pursuit disorders, vergence abnormalities, nystagmus, and ocular oscillations. Supranuclear disorders result from lesions above the level of the ocular motor nerve nuclei. If oculocephalic maneuvers move the eyes appropriately, the lesion causing the gaze palsy is supranuclear. Supranuclear disorders account for almost 10% of all patients with disorders of eye movements.