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Biomedical subjects

T R Hedges

Publications and source records attributed to T R Hedges.

At least 37 records · Page 2Linked to original sources
PubMed1995

Extinction during time controlled direct retinal stimulation after recovery from right hemispheric stroke.

The temporal variables of extinction in two patients with right hemispheric stroke and two normal controls were studied using a scanning laser ophthalmoscope (SLO). This instrument enabled eye movements to be controlled for by projecting time controlled stimuli directly on to the retina. Both patients had recovered from their stroke (four months and five years) and seemed clinically normal. At 50 ms, patient 1 extinguished one of two stimuli on seven of 40 double simultaneous stimulation (DSS) trials (five left, two right) and patient 2 extinguished the left stimulus on every DSS trial. At 100 ms, patient 1 performed almost perfectly, whereas patient 2 extinguished on 30% of the DSS trials (10 left, two right). At 200 ms, patient 2 performed perfectly. Neither of the controls showed extinction to DSS at any presentation time. Thus detecting DSS was time dependent in the patients but not the normal subjects. These data support the theory that recovery from neglect after right hemispheric damage may be mediated by the left hemisphere.

Adult↗
PubMed1994

Mitochondrial DNA mutations in Cuban optic and peripheral neuropathy.

OBJECTIVE: To investigate the potential role of mitochondrial DNA (mtDNA) mutations in the recent outbreak in Cuba of optic neuropathy and peripheral neuropathy (COPN). DESIGN AND METHODS: Historical features were reviewed and neuro-ophthalmologic examinations were performed on a sample of COPN patients (n = 9) and Cuban patients with other forms of optic neuropathy (n = 2). Molecular genetic methods were then used to test for the presence of 9 mtDNA mutations that were previously associated with Leber's hereditary optic neuropathy (LHON). RESULTS: Two (22%) of 9 COPN patients harbored an LHON-associated mtDNA mutation at nucleotide position 9438 and a novel mutation at nucleotide position 9738 in the cytochrome c oxidase subunit III gene. None of the Cuban patients harbored any of the 8 other LHON-associated mtDNA mutations. Detailed sequence analysis revealed that the Cuban patients could be divided into 7 distinct mtDNA haplotypes and that the 2 COPN patients with mtDNA mutations in the cytochrome c oxidase subunit III gene were not members of the same maternal lineage. CONCLUSIONS: The pathogenesis of epidemic COPN is likely complex and multifactorial. Our preliminary results in a small sample of Cuban patients suggest that mtDNA mutations may play a role in some cases. mtDNA mutations may render an individual genetically susceptible to a variety of factors that impair oxidative phosphorylation, including nutritional deficiency, tobacco, alcohol, and other toxins.

Adult↗
PubMed1994

The retinal venous pulse. Its relation to optic disc characteristics and choroidal pulse.

PURPOSE: The presence or absence of the spontaneous retinal venous pulse is an important clinical sign, especially when one is evaluating a patient who may have increased intracranial pressure. The purpose of this study is to evaluate a large group of healthy patients, correlating optic disc characteristics, choroidal pulse, and brachial pulse pressure with the presence and intensity of the spontaneous retinal venous pulse. METHODS: Ninety-seven patients were studied correlating these parameters with their fundus photographs. Ocular pneumotonometry as a measure of the choroidal pulse and the brachial pulse pressure were correlated with the optic disc characteristics and the intensity of the retinal venous pulse statistically. RESULTS: The results showed a highly significant correlation with these parameters. The greater the pulse amplitude--especially the choroidal pulse the more likely the spontaneous retinal venous pulse would be present. More importantly, the anatomic variable of optic disc cup and vascular configuration had the greatest influence on whether the spontaneous retinal venous pulse is present or absent. CONCLUSION: The authors conclude that unless the clinician is aware of the importance of optic nerve characteristics and pulse amplitude in the choroid (indirectly measured in a normal clinical setting by the brachial pulse) the significance of the spontaneous retinal venous pulse cannot be properly determined.

Adolescent↗
PubMed1993

Optic nerve decompression improves hemodynamic parameters in papilledema.

PURPOSE: The purpose of this study is to examine changes in color Doppler imaging parameters before and after optic nerve sheath decompression (ONSD) for chronic papilledema caused by pseudotumor cerebri (PTC). METHODS: Color Doppler imaging was performed within 48 hours before surgery and within 48 hours after the procedure using a color Doppler unit with a 7.5-MHz phased linear transducer. Pulsed Doppler spectrum analyses were recorded digitally on videotape from the ophthalmic, central retinal, and short posterior ciliary arteries, using a 0.4 x 0.6-mm sample volume. RESULTS: Blood flow velocities in the ophthalmic, short posterior ciliary, and central retinal arteries of 24 eyes were significantly decreased compared with a healthy age-matched group. Eyes with visual acuities worse than 20/30 before surgery had significantly decreased velocities in the ophthalmic, short posterior ciliary, and retinal arteries, whereas in eyes with visual acuities better than 20/30, only the short posterior ciliary and central retinal arteries demonstrated decreased velocities. In addition, Gosling's pulsatility index was increased for the central retinal artery but not the ophthalmic or short posterior ciliary arteries. Thirteen eyes improving in visual acuity and field after ONSD demonstrated significant improvement in all color Doppler imaging parameters for the short posterior ciliary arteries. The ophthalmic artery diastolic velocity also increased significantly but the central retinal artery parameters did not change. The eyes that remained stable or worsened did not demonstrate significant postoperative changes. CONCLUSION: These results suggest that some of the visual loss from chronic papilledema may be due to ischemia, and worsening visual acuity correlates with greater impairment of the retrobulbar circulation. One of the mechanisms by which ONSD improves visual function may be reversal of this ischemic process.

Arteries↗
PubMed1993

Food shortages and an epidemic of optic and peripheral neuropathy in Cuba.

From late 1991 to mid-1993, cases of optic neuropathy of unknown etiology, which first appeared in unusual numbers in a western province of Cuba, spread and multiplied throughout the island. The dominant symptoms changed, becoming increasingly those of peripheral neuropathy. Incidence rates peaked in April 1993. An estimated 50,000 cases were reported. The majority were adult men and women (aged about 25-65), with comparatively few children or elderly people being affected. The cause has yet to be delineated. However, food shortages and radical changes in diet resulting from the longstanding US trade embargo and the recent loss of Eastern Europe as Cuba's trading partner have compromised nutritional status, especially B-vitamin sufficiency, and appear to be related to the neuropathic illnesses. In April 1993, the Cuban government began distributing vitamin supplements to every citizen. Causal hypotheses include tobacco-alcohol or "nutritional" amblyopia; cyanide toxicity from cassava; toxic legumes introduced as supplements to scarce flour; other toxins, for example pesticides, or a "blue mold" on tobacco; enterovirus; and a hereditary enzyme deficiency in affected persons. None of these factors appears to be present in all cases, but it is generally believed that an interaction of some toxin or toxins, in combination with nutritional deficiency, is likely to be the major cause.

Adult↗
PubMed1993

Intermittent downbeat nystagmus due to vertebral artery compression.

Downbeat nystagmus (DBN) uncommonly occurs as a transient phenomenon, and it rarely occurs in patients with cerebrovascular disease. We observed a patient with intermittent DBN and lightheadedness due to transient obstruction of his dominant vertebral artery when he turned his head to his left side. Surgical removal of an osteophyte at the site of the angiographically demonstrated lesion relieved his symptoms.

Cervical Vertebrae↗
PubMed1992

Periodic alternating gaze deviation in infancy.

Periodic alternating gaze is a rarely reported phenomenon. We have observed two cases that are unique in their early onset at birth and infancy. Multiple congenital defects of the posterior cranial fossa were present on MRI in both cases. A prominent abnormality shared by both was absence of normal structures in the region of the inferior cerebellar vermis. Periodic alternating gaze appears to be associated with pathologic changes in the hindbrain in these and other reported cases.

Brain↗
PubMed1992

Surgical reversal of a subacute complete unilateral visual loss from an ovarian metastasis to the pituitary gland.

A 56-year-old woman with ovarian papillary cystadenocarcinoma that metastasized to the pituitary gland sought treatment with a 7-day history of total loss of vision in one eye. Ten days after transsphenoidal tumor resection, the patient's vision suddenly returned to baseline. This unusual case indicates that surgical decompression of the optic nerve and chiasm can completely salvage vision, even after prolonged total visual loss.

Blindness↗
PubMed1990

Neuro-ophthalmologic manifestations of Lyme disease.

Lyme disease is a tick-borne spirochetal infection characterized by skin rash, neurologic, cardiac, and arthritic findings. The authors report six patients with Lyme disease who had neuro-ophthalmologic manifestations. One patient had meningitis with papilledema, two had optic neuritis, and one had neuroretinitis. Three patients had sixth nerve paresis, two of whom cleared quickly, whereas multiple cranial nerve palsies and subsequent optic neuropathy developed in another. Early recognition of neuro-ophthalmologic findings can help in the diagnosis and treatment of Lyme disease.

Abducens Nerve↗
PubMed1989

Metamorphopsia and palinopsia. Association with periodic lateralized epileptiform discharges in a patient with malignant astrocytoma.

A patient with a right parietal glioma developed palinopsia and various forms of metamorphopsia that were temporally related to the electrographic presence of periodic lateralized epileptiform discharges. These symptoms occurred in an alert woman with normal visual fields. The literature shows that epileptic events can produce these symptoms. We believe that continuous repetitive electrical stimulation caused our patient's unusual symptoms by altering the association pathways through which visual data are experienced. To our knowledge, the association between periodic lateralized epileptiform discharges and metamorphopsia or palinopsia has heretofore not been reported.

Adult↗
PubMed1989

Encephalopathy, deafness and blindness in young women: a distinct retinocochleocerebral arteriolopathy?

Three young women (aged 18 years, 19 years and 19 years) who developed progressive neuropsychic and neurologic disturbances with hearing loss and multifocal retinal artery branch occlusions are reported. This retinocochleocerebral syndrome has been reported previously only in 12 young North American women. Its pathogenesis is unknown, but an atypical viral infection of the vessel walls has been suggested. Abnormalities of T lymphocytes subsets in blood in one of the patients suggested an immunological dysfunction, but all other tests, including immunological reactions on brain and skin biopsies, were negative or non-specific. Steroids and immunosuppressive agents have been advocated on an empirical basis, but the second patient showed a substantial recovery without any therapy and the third gradually deteriorated despite azathioprine, cyclophosphamide, prednisone and plasma exchanges. This retinocochleocerebral syndrome probably corresponds to an arteriolopathy of unknown nature.

Adolescent↗
PubMed1989

Occipital infarction with hemianopsia from carotid occlusive disease.

Extracranial internal carotid artery occlusive disease usually produces stroke in the middle cerebral artery territory or the border zone between the middle and anterior cerebral arteries. It is unusual for occipital infarction in the posterior cerebral artery territory to be caused by internal carotid artery disease despite the fact that the posterior cerebral artery may arise directly from the internal carotid artery as an anatomic variation. We describe a patient with a fetal posterior cerebral artery originating from the internal carotid artery, and the initial manifestation of his extracranial internal carotid artery occlusive disease was hemianopsia from occipital infarction.

Aged↗