Mark L. Moster

Topography of scalp potentials preceding self‐initiated saccades

We studied 3 scalp potentials recorded prior to saccades in relation to visual targets (the presaccadic negativity [PSN], presaccadic positivity [PSP], and spike potential [SP]) in normal subjects performing self-initiated saccades in darkness. There was a prominent PSN beginning at −800 msec, maximal at the vertex. This finding is consistent with activation of the supplementary eye field in the anterior mesial frontal cortex, a concept which correlates with cortical neuron recordings in monkeys and cerebral blood flow studies in humans. A widespread PSP, with greatest amplitude over the posterior scalp, suggests parieto-occipital participation even in the absence of visual targets. The sharp character of SP with focal lateralized frontal negativity, its “mirror image” scalp distribution when comparing leftward to rightward saccades, and its timing near the onset of saccades support an origin near the orbit, in either ocular motor nerves or muscles.

Gadolinium-DTPA-enhanced magnetic resonance imaging in optic neuropathies.

Magnetic resonance imaging (MRI), after intravenous administration of the paramagnetic agent gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), showed enhancement of the optic nerve in 7 of 13 patients with acute optic neuritis. Four of these patients had Gd-DTPA enhancement of the intracranial optic nerve and two had involvement of the optic nerve at the orbital apex, ipsilateral to the eye with visual loss. Gadolinium-DTPA enhancement of both intracranial optic nerves was seen in one of two patients with bilateral retrobulbar neuritis. Two patients with acute radiation-induced optic neuropathy also had Gd-DTPA enhancement of the intracranial optic nerve. The authors recommend MRI with Gd-DTPA as the neuro-diagnostic procedure of choice for visualization of increased permeability of the blood-brain barrier in acute optic neuritis and radiation-induced optic neuropathy.

Giant Cell Arteritis in the Ocular Ischemic Syndrome

Oculomotor nerve paresis, ocular hypotony, anterior segment ischemia, and the ocular ischemic syndrome are uncommon manifestations of giant cell arteritis. Four patients with these findings had giant cell arteritis documented by temporal artery biopsy. Cerebral angiography or ultrasonography, or both, performed in three patients, excluded hemodynamically significant stenosis of the internal carotid artery as the cause of ocular ischemia and cerebral aneurysms as the cause of oculomotor nerve paresis. Corticosteroid treatment, administered to three patients, resulted in resolution of the oculomotor deficits and the clinical signs of ocular ischemia, although the visual acuity in one patient improved from 20/400 to 20/60. Giant cell arteritis should be considered in the differential diagnosis of the ocular ischemic syndrome.

Isolated trochlear nerve palsy in patients with multiple sclerosis

To the Editor: We read with interest the report of Currier and Bebin1 describing five patients with wild arm ataxia following lateral medullary infarction. Neuropathologic findings were presented for a 74-year-old man who had “experienced two respiratory arrests and died” 5 or more days following the onset of stroke symptoms. The cause of his death was stated to be “a completely thrombosed right vertebral artery.” We noticed that this vascular lesion together with the right lateral medullary infarction described are not typically lethal in themselves. Recent reports2-5 have described patients who experienced unexpected sudden cardiorespiratory arrest several days following lateral medullary infarction, at a time when they were convalescing well and were medically and neurologically stable following a stroke that caused minimal motor disability. One report2 mentions a patient who survived a first cardiorespiratory arrest before experiencing a second arrest 3 days later. None of these reports mentions neurologic sequelae suggestive of wild arm ataxia, thereby diminishing the likelihood that wild arm ataxia might have predictive value for sudden cardiorespiratory arrest. The reports have speculated on mechanisms by which cardiorespiratory arrest occurred; cardiac arrhythmia is among these.4 Although we do not know many of the details surrounding the death of the 74-year-old man described by Currier and Bebin,1 we speculate that his death may have been caused by an intermediate event in which the lateral medullary infarction and surrounding brain tissue disturbance (possibly ischemic penumbra) influenced brainstem cardiac and respiratory centers together with autonomic pathways in a manner that at this time is not understood. It is interesting that the small collection of anecdotal reports2-5 describing this phenomenon is beginning to interface with another collection of reports6-8 describing unexpected sudden death in patients who were found at autopsy to have primary brain tumors infiltrating or compressing the medulla. Some of these patients had been considered neurologically normal and were unaware of their tumors.6 Others7,8 had various medical problems that were seen in hindsight as related to their tumors, which were not definitively diagnosed during life. In speculating about the mechanism of unexpected sudden death, the authors of these reports have all focused on involvement of the medullary respiratory centers. Because some medullary infarctions may present with symptoms suggestive of non-neurologic disease,9 and some medullary tumors may be asymptomatic for extended periods of time,6 all unexpected sudden deaths with otherwise unexplained etiologies need to be investigated by an autopsy inclusive of a careful neuropathologic examination in order to exclude the possibility of these medullary lesions.

Successful Management of a Pregnant Woman with a TSH Secreting Pituitary Adenoma with Surgical and Medical Therapy

We described a 39-yr-old asian female who was initially diagnosed with prolactinoma and presented with increase nervousness and weight loss. Laboratory evaluation revealed an inappropriately normal TSH level with elevated free T4, total T3, α-subunit and prolactin level. The α-subunit/TSH molar ratio was 4. MRI showed a macroadenoma extending to the suprasellar cistern. Treatment was begun with propylthiouracil and bromocriptine. After 5 months of therapy, she became pregnant.At 27 weeks of gestation, she developed headache and decreased visual acuity in her left eye. MRI showed a slightly increase in tumor size compressing the optic chaiasm. Transphenoid macroadenectomy was performed with immediate relief of the visual field abnormality. At 39 weeks gestation a baby with no malformations was delivered. This is the second case report of TSH secreting pituitary adenoma which was exarcerbated during pregnancy. In contrast to the first case, our case was managed with both surgical and medical approach. The judicious use of both medical and surgical therapy can result in a successful outcome to mother and fetus in a patient with TSH secreting pituitary adenoma.

Coagulopathies and arterial stroke.

Although hypercoagulable states are most often associated with venous thrombosis, arterial thromboses are reported in protein S, protein C, and antithrombin III deficiencies, factor V Leiden and prothrombin gene mutations, hyperhomocysteinemia, dysfibrinogenemia, plasminogen deficiency, sickle cell disease, and antiphospholipid antibody syndrome.

Evidence for widespread structural brain changes in glaucoma: a preliminary voxel-based MRI study.

PURPOSE To investigate structural brain changes in patients with glaucoma. METHODS High-resolution T1-weighted anatomical brain magnetic resonance images (MRI) were collected in 15 patients with glaucoma of varying severity and in 15 age-, race-, and sex-matched controls. Exclusion criteria included neurological disease, another disorder which could affect the visual field, and a score of less than 25 on the mini-mental status examination. The scans were analyzed with an automatic volumetric MRI technique to measure the volumes of 93 structures in each brain. Analyses of covariance with age as a covariate were carried out to identify structures that differed significantly between the two groups (i.e., glaucoma versus normal control). The volumes of all brain structures in the group of 15 glaucoma patients were also correlated with clinical measures of disease severity. Linear multivariate regression analyses were conducted to determine the significance of these relationships. RESULTS Five structures differed significantly between the two groups (P < 0.05). These structures included the right and left inferior occipital gyri and the right middle occipital gyrus, right inferior temporal gyrus, and right occipital lobe white matter. Interestingly, all of these structures were larger in the glaucoma group than in the control group. Within the group of glaucoma patients, 38% of all brain structures had independent associations between decreasing volume and more severe disease in multivariate regression analysis. CONCLUSIONS These results suggest that patients with glaucoma undergo widespread and complex changes in cortical brain structure and that the extent of these changes correlates with disease severity.

Functional Visual Loss in Idiopathic Intracranial Hypertension

OBJECTIVE To identify and describe patients with idiopathic intracranial hypertension (IIH) with concurrent functional visual loss (FVL). DESIGN Observational, retrospective case series. PARTICIPANTS Seventeen patients with IIH and FVL. METHODS Clinical features were collected retrospectively. Data from 281 cases of IIH were analyzed for concurrence of FVL. MAIN OUTCOME MEASURES Occurrence of FVL diagnosed at presentation or on subsequent follow-up. RESULTS Seventeen patients had FVL and IIH. Of the 17 patients with FVL and IIH, 11 (65%) had FVL on presentation, with the remaining 6 patients developing FVL after initial presentation. Two patients in this cohort had documented recurrence of their IIH. There were several common patterns of FVL. All 17 patients had functional visual fields, with 82% having tubular fields and 71% exhibiting nonphysiologic constriction on perimetry testing. Seventy-six percent of patients had nerve/field mismatch showing no atrophic disc changes. Eighty-eight percent of patients had significant psychiatric, psychosocial, or other medical comorbidities. The majority of patients were managed surgically at some point in their clinical history, with 53% having nerve decompression, shunt, or both. Three patients had optic nerve sheath fenestrations after the diagnosis of FVL. CONCLUSIONS Results suggest a high prevalence of FVL in IIH with a potential association with psychiatric illness and psychosocial stressors requiring careful consideration before surgical intervention. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Abnormal Function of the Parvocellular Visual System in Anisometropic Amblyopia

PURPOSE To study the function of the parvocellular (P) and the magnocellular (M) visual systems with steady-state visual evoked potentials (VEPs) in anisometropic amblyopes. METHODS A matrix of isolated checks was superimposed on a steady background with different check sizes and temporal frequencies to form specific stimuli to preferentially activate the P or the M visual system. The amplitude of the VEP fundamental frequency was analyzed at the electrode Oz of 5 anisometropic amblyopes and 22 normal subjects. The normal subjects were tested at two visual acuity (VA) levels, 20/20 and 20/40, modified by lenses, to match with the VA levels of the fellow eyes and the amblyopic eyes of the amblyopes, respectively. RESULTS No significant amplitude difference was found between the dominant eyes and nondominant eyes of the normal subjects for either P or M stimuli at both 20/20 and 20/40 VA levels (P>.05). No significant amplitude difference was found between the fellow eyes of the amblyopes and the dominant eyes of normals for either P or M stimuli at 20/20 VA level (P>.05). A significant amplitude difference was found between the amblyopic eyes and the nondominant eyes of the normals for P stimuli (P<.05) but not for M stimuli (P>.05) at 20/40 VA level. CONCLUSIONS The amplitude of the VEP fundamental frequency was selectively reduced for P stimuli in anisometropic amblyopic eyes. This clinical electrophysiologic finding confirms that only the function of the P visual system is abnormal in anisometropic amblyopic eyes.

Intracranial malignancies occurring more than 20 years after radiation therapy for pituitary adenoma

A 37-year-old woman developed a left third cranial nerve palsy 28 years after radiation for a nonsecreting pituitary adenoma. Imaging disclosed a left parasellar mass and a midbrain/pontine signal abnormality. Biopsy of the parasellar mass revealed a malignant sarcoma. The brainstem abnormality was presumptively diagnosed as a malignant glioma. A 63-year-old man developed a malignant astrocytoma of the left optic nerve and chiasm 23 years after partial excision and radiation of a nonsecreting pituitary adenoma. Both patients died of their malignancies. Although secondary malignancies have been described in this setting, such long latencies have not been reported.