The effect of the sequence of contralateral cortical and collicular lesions on the rate of relearning a visual discrimination by cats.

Visual field deficits which follow ablation of the posterior two-thirds of one cerebral hemisphere in the cat have been shown to be ameliorated by ablation of the contralateral superior colliculus. The present study was designed to determine whether the sequence in which contralateral cortical and collicular lesions are made is a significant factor affecting the rate of monocular relearning through the eye ipsilateral to the cortical lesion. Nine adult cats had the optic chiasm sectioned, were trained to criterion monocularly on a dark-light discrimination, and were divided into two groups. Four cats (Group S) had one superior colliculus ablated, followed one month later by ablation of the contralateral two-thirds of the neocortex. Five cats (Group C) had the same lesions in the reverse order. One month after the second brain lesion, each cat was retrained monocularly through each eye on the dark-light discrimination for food reward in a Y-maze. Through the eye ipsilateral to the cortical lesion, all cats in Group S relearned to criterion more rapidly than cats previously reported with only unilateral neocortical lesions. Four of the five cats in Group C were severely retarded in relearning and two of these cats failed to relearn. The results show that when chiasm-sectioned cats are trained monocularly in a Y-maze on a dark-light discrimination, ablation of the superior colliculus prior to ablation of the contralateral neocortex facilitates relearning through the eye ipsilateral to the cortical ablation. When ablation of the superior colliculus follows the neocortical lesion, learning occurs but is not facilitated by the additional lesion.

Optic chiasmal neuritis.

In four of six patients with clinical optic chiasmal neuritis, MRI demonstrated abnormalities of the chiasm. Optic chiasmal neuritis may be the initial manifestation of multiple sclerosis, a reflection of established CNS demyelination, or an isolated clinical finding.

Objective evaluation of improvement in optic neuropathy following radiation therapy for thyroid eye disease.

PURPOSE: While the literature supports the use of radiation therapy for thyroid eye disease, it does not sufficiently describe in detail the results of radiation therapy for optic neuropathy associated with thyroid eye disease. The objective of this study is to quantify the changes in parameters of optic neuropathy after orbital irradiation for thyroid eye disease. METHODS AND MATERIALS: Twelve consecutive patients with optic neuropathy from thyroid eye disease were followed by a single neuro-ophthalmology practice and treated by one radiation oncologist with radiation therapy from 1991 through 1995. All cases were prospectively followed for visual acuity, color vision, mean deviation, and/or foveal sensitivity and afferent pupillary defect. All patients received 2000 cGy in 10 fractions with megavoltage irradiation to the orbits. RESULTS: Ten of 12 patients were evaluated for follow-up (one moved out of this country and one had a stroke, which confounded interpretation of examination results). An analysis was performed retrospectively while treatment and evaluation remained uniform. Five men and five women formed the basis of this study with a median age of 60 years (35-76 years). Nineteen eyes were evaluated for thyroid optic neuropathy. Improvement in optic nerve function occurred in eight of ten patients. Improvement was seen either during radiotherapy or within 2 weeks of completion. No long-term adverse effects were noted. CONCLUSION: This study objectively demonstrates improvement in optic neuropathy from radiation therapy for thyroid eye disease.

24-hour blood pressure monitoring in patients with anterior ischemic optic neuropathy.

OBJECTIVE: To define parameters of ambulatory diurnal blood pressure in patients who had experienced anterior ischemic optic neuropathy (AION) in a case-controlled study. PARTICIPANTS AND METHODS: Twenty-four patients with AION and 24 control subjects who were matched for age, gender, medical diagnoses, and medications underwent ambulatory automated blood pressure monitoring for 24 hours. RESULTS: The overall diurnal pattern of blood pressure appeared to be normal in all subjects, showing lower blood pressures at night than during the day, an overnight nadir, and an ascending blood pressure curve in the morning to reach daytime levels. Also, patients with AION did not differ from control subjects with respect to the nighttime diastolic nadir or daytime peak systolic blood pressure. However, during the daytime, patients with AION had lower mean systolic and diastolic blood pressures than did matched control subjects. The widest difference between their blood pressure curves occurred after awakening in the morning, when patients with AION had a less steep and more irregular rise of blood pressure. Patients who had signs of vertebrobasilar insufficiency in addition to AION had lower mean diastolic blood pressure during both daytime and nighttime and a lower minimum daytime diastolic blood pressure. CONCLUSIONS: On ambulatory measurements of diurnal blood pressure, patients with AION consistently had a lower mean blood pressure than did control subjects and a lag in the usual rise in blood pressure in the morning to meet increasing daytime demands for perfusion. Chronic hypoperfusion of small end-arterial vessels that supply the optic nerve head may predispose to AION, and may be caused by relative hypotension owing to overtreated hypertension or to abnormal vascular autoregulation. Internists should be asked to monitor blood pressure carefully when treating hypertensive patients who are at risk for AION, to avoid hypotension, especially on awakening in the morning.

Peripapillary hemorrhage.

On routine examination, a 61-year-old man was found to have a deep peripapillary hemorrhage surrounding his left optic nerve head. Further examination revealed a left sixth nerve paresis, a subtle right homonymous quadrantanopia, and jerky pursuit to the left. The diagnostic work-up was delayed by the patient because of business commitments. He returned confused and obtunded. Neuro-imaging showed a large frontal mass, which turned out to be an anaplastic astrocytoma. Diagnosis of the lesion had been obscured by three false localizing signs. Discussion deals with the definition of Terson's syndrome and the occurrence of peripapillary hemorrhages. Other causes of peripapillary hemorrhages are illustrated.

Lyme disease: neurologic and ophthalmic manifestations.

Lyme disease is tick-borne infection which produces early and late manifestations in many organ systems. Prominent symptoms and signs occur in skin, heart, joints and nervous system. Many ocular and neuro-ophthalmic abnormalities recently have been attributed to Lyme disease, but some cases have not been well established as direct sequelae. This review of the contemporary state of knowledge about Lyme disease was undertaken so that more rigorous criteria can be applied in future diagnosis.

Visual discrimination between spatially separated stimuli by cats with lesions of the superior colliculus-pretectum.

(1) This study was designed to test the ability of cats with lesions of the superior colliculus-pretectum to discriminate between stimuli which are widely separated in space. (2) Intact cats and cats learning or relearning after lesions of the superior colliculus-pretectum, were trained on light-dark (LD) and horizontal-vertical stripe (HV) discriminations in a V-maze, where the stimuli were widely separated in space, or in a divided straight maze, where the stimuli were side by side. (3) Two types of errors were scored: door-push errors when the cat pushed open the incorrect door; alley-entrance errors when the cat entered the incorrect alley, but turned and entered the correct alley without having pushed the incorrect door. (4) In the V-maze as well as in the straight maze, cats with lesions of the superior colliculus-pretectum achieved criterional performance by alley-entrance and door-push scoring on LD and HV discriminations. Thus, cats with lesions of the superior colliculus-pretectum can locate or orient to widely separated visual stimuli well enough to discriminate between them from a distant choicepoint. (5) Cats with lesions of the superior colliculus-pretectum generally committed a larger number and higher percentage of alley-entrance errors during learning than unoperated cats in either maze. However, commission of alley-entrance errors was not further increased in the V-maze, where the stimuli were widely separated in space. (6) All unoperated cats committed alley-entrance errors as well as door-push errors suggesting that commission of alley-entrance errors may reflect a normal process in two-choice learning.

Deficits in luminous flux discimination by cats with lesions of the superior colliculus-pretectum.

(1) Intact cats and cats relearning or initially learning after bilateral ablation of the superior colliculus-pretectum were trained on a simple flux discrimination in a straight maze where the stimuli were either immediately side by side at the end of the runway or were separated by an opaque barrier. (2) After ablation of the superior colliculus-pretectum, each preoperatively trained cat had a significant deficit in retention of the luminous flux discrimination regardless of whether or not the stimuli were separated by a barrier or whether the correct stimulus was darker or lighter than the incorrect stimulus. (3) Under each of the different training conditions, every cat learning the flux discrimination initially after ablation of the superior colliculus-pretectum was retarded in comparison with intact cats. (4) The severity of the postoperative learning deficit correlated highly with the total extent of the lesion in the superior colliculus and pretectum.

Distractibility of cats with lesions of the superior colliculus-pretectum during performance of a 4-choice visual discrimination.

(1) Intact cats and cats with bilateral lesions of the superior colliculus-pretectum were trained on 4-choice, luminous flux discriminations in an apparatus consisting of a 6-foot square open field with 4 stimulus panels along one wall. After cats attained a high performance criterion on a 4-choice dark-light discrimination they were tested for 'distractibility' by flashing a light behind one of the stimulus panels. (2) All intact cats and cats with lesions of the superior colliculus-pretectum learned the 4-choice luminous flux discriminations. Cats with lesions of the superior colliculus-pretectum, however, followed longer paths and had longer latencies to the correct door, even after attaining criterional performance. (3) All intact cats and cats with lesions of the superior colliculus-pretectum were distracted by the flashing light, as indicated by increased commission of errors, increased path lengths and increased response latencies on trials in which the distracting stimulus was presented. However, both intact cats and cats with lesions of the superior colliculus-pretectum habituated to the distracting stimulus. (4) These results are consistent with previous findings that cats with lesions of the superior colliculus-pretectum have difficulty in withholding incorrect responses or in shifting attention or response tendencies from the incorrect to the correct stimulus. (5) These results do not support the hypothesis that lesions of the superior colliculus produce deficits in attention as measured by distractibility to novel stimuli.

Hemianopic visual field defects in children with intracranial shunts: report of two cases.

OBJECTIVE AND IMPORTANCE: Intracranial shunts are commonly placed in children and frequently require replacement during the child's growing years. Severe signs of increased intracranial pressure often are the first indication of shunt displacement and malfunction. Subtle neuro-ophthalmic signs in children are usually overlooked. CLINICAL PRESENTATION: Two cases are described in which homonymous hemianopsia resulted from unsuspected movement of the shunt catheter in growing children. In one male patient, the catheter tip impaled the optic tract, and in the other male patient the shunt became embedded in the midbrain tegmentum and shunt failure led to compression of the posterior cerebral artery. INTERVENTION: In the presence of optic atrophy, papilledema may go unnoticed without serial examinations. This stresses the importance of detecting other early warning signs of shunt displacement and increased intracranial pressure, including visual field changes and subtle abnormalities of motility. CONCLUSION: Because early diagnosis and shunt revision may allow visual recovery, children with shunts should be followed with visual fields and serial disc photographs.

Resolution of chronic cluster headache after resection of a tentorial meningioma: case report.

Cluster headache is almost always idiopathic, but, in rare cases, associated intracranial lesions have been found. We describe a patient who had chronic cluster headache for more than 20 years. The headache immediately resolved upon resection of a tentorial meningioma. Prior reports of cluster headache as a manifestation of structural disease are briefly reviewed. In the patient described, the pain was referred from the right tentorium cerebelli to the right side of the face, in accordance with reported studies on the subjective localization of pain referred from posterior fossa structures. The accompanying abnormalities of autonomic function may have been mediated by central autonomic reflexes that are also involved in the pathogenesis of idiopathic cluster headache.

Deficits in visual learning by cats with lesions of the visual cortex.

Cats were trained for food reward in a divided straight maze or in a V-maze on a light-dark discrimination and on a series of horizontal-vertical stripe discriminations. Errors were scored by both door-push and alley-entrance criteria. After lesions of the visual cortex, cats could relearn or initially learn the light-dark discrimination but were not successfully trained to shift from brightness to pattern cues when learning the series of horizontal-vertical stripe discriminations, using a modified method of limits procedure. Both unoperated cats and cats with lesions of the visual cortex committed alley-entrance errors when learning the light-dark discrimination.

Recurrent attacks of amaurosis fugax treated with calcium channel blocker.

Vasospasm may be one of the causes of amaurosis fugax. A patient is reported who daily experienced multiple brief episodes of amaurosis fugax. The absence of physical, laboratory, or radiographic evidence for thromboembolism, hemodynamic compromise, or vasculitis, suggested that the amaurosis might be caused by vasospasm. This hypothesis was supported by cessation of the attacks of amaurosis when the patient was treated with a calcium channel blocker.

Relative pupil-sparing oculomotor nerve palsy as the presenting sign of posterior fossa meningioma.

We report a case of relative pupil-sparing oculomotor paresis initially attributed to ischemia because weakness of other cranial nerves was minimal and dismissed as insignificant. Neuroimaging eventually revealed a posterior fossa meningioma. The neurologic symptoms and signs disappeared immediately after resection of the tumor. The third nerve palsy was attributed to deformation of the brainstem. This case reinforces the importance of neuroimaging even in patients who have apparently isolated oculomotor palsy with features not classic for an ischemic etiology.

Recovery from ocular ischemic syndrome after treatment with verapamil.

Vasospasm has been implicated as a cause of amaurosis fugax, which can be controlled by administration of the calcium channel blockers nifedipine or verapamil. However, vasospasm has not previously been thought to be involved in chronic ocular ischemia. We report a patient with ocular ischemic syndrome, which may have had vasospasm as a contributing cause, since the patient also developed amaurosis fugax despite daily aspirin therapy. An 80-year-old man with chronic open-angle glaucoma developed chronic ocular ischemia characterized by progressively decreased visual acuity, pain, rubeosis, and hypotony, as well as transient visual dimming. Medical evaluation revealed no evidence of carotid stenosis, thromboembolism, or vasculitis as the cause of ocular ischemia. When the calcium channel blocker verapamil was administered, the episodes of transient visual dimming ceased immediately. In addition, soon thereafter, visual acuity improved, the rubeosis partially regressed, and the hypotony reversed. This case indicates that the calcium channel blocker verapamil may be effective in treating cases of ocular ischemic syndrome, when vasospasm is a contributing cause.