The patient is examined in a dim room and fixation is directed to a distant target. The flashlight is swung briskly over the bridge of the nose to the eye with the defective optic nerve. The abnormal pupil remains momentarily constricted from the lingering effects of the consensual light response. However, the impaired eye with its reduced pupillomotor signal soon escapes the consensual reflex and actually dilates despite being directly stimulated with light. The pupil that paradoxically dilates to direct light stimulation displays the afferent defect .
Myoclonus is sudden shock-like muscular twitches of the face, limbs, or trunk.
The etiology of the clinical syndrome may be direct viral invasion, postinfecitious encephalopathy, or neuroblastoma. The adrenal medulla and sympatic chain in the abdomen or chest are common sites of origin of a neuroblastoma. Determination of urinary excretion or catecholamine metabolites is a useful screening test. CT scan of the abdomen may also detect the presence of a malignant mass. If there is a strong clinical suspicion of pheochromocytoma, complete workup would include VMA spot test, complete blood count, IVP, chest x-ray, skeletal survey, bone marrow aspiration and bone scan.