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Biomedical subjects

C Chalk

Publications and source records attributed to C Chalk.

13 recordsLinked to original sources
PubMed2003

Non-24-hour sleep-wake syndrome following a car accident.

The authors report the case of a 39-year-old sighted woman who displayed non-24-hour sleep-wake cycles following a car accident. The phase relationship between endogenous circadian markers such as plasma melatonin and 6-sulfatoxymelatonin rhythms and self-selected sleep times was abnormal. A laboratory investigation indicated that she was sensitive to bright light as a circadian synchronizer. MRI and brain CT scans were normal, but microscopic brain damage in the vicinity of the suprachiasmatic nucleus or its output pathways is plausible.

Accidents, Traffic↗
PubMed2000

Impact of plasma exchange on indices of demyelination in chronic inflammatory demyelinating polyradiculoneuropathy.

We studied the impact of plasma exchange (PE) on indices of primary demyelination in patients of the Canadian multicenter trial of PE in chronic inflammatory demyelinating polyneuropathy (CIDP). Individual motor nerves (median, ulnar, peroneal, tibial) were studied: distal motor latencies (DMLs), proximal and distal compound muscle action potential (M-wave) amplitudes, negative peak areas and durations, and motor conduction velocities (CVs). Proximal M-wave amplitudes in individual motor territories, particularly in the ulnar nerve (from below elbow, above elbow, and axillary stimulating sites) demonstrated significant improvement with PE, but not sham exchange. Proximal ulnar M-wave areas also had significant improvement with PE. Trends toward improvement of individual nerve motor CVs, M-wave durations, and DMLs did not achieve statistical significance. Proximal M-wave amplitudes, particularly in the ulnar motor territory, and proximal M-wave areas (providing a measure of conduction block) were the most sensitive indices of improvement conferred by PE in CIDP. In individual patients, these indices may help judge the efficacy of therapy.

Action Potentials↗
PubMed1999

Isolated trigeminal neuropathy due to trigeminal nerve root hemorrhage.

BACKGROUND: Isolated trigeminal neuropathy is uncommon; causes include trauma, inflammation, or neoplasm. METHODS: We report a patient who fell and struck his head during a myocardial infarction, was treated with streptokinase, and developed symptoms and signs of an isolated trigeminal sensory neuropathy. RESULTS: Imaging showed hemorrhage in the trigeminal nerve root; follow-up imaging showed resolution of the hemorrhage, but no underlying structural lesion. CONCLUSION: A combination of head trauma plus thrombolysis resulted in an isolated trigeminal neuropathy.

Cerebral Hemorrhage↗
PubMed1998

Trigeminal nerve hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy.

An unusual clinical manifestation of nerve hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is described. A patient with a 13-year history of CIDP developed diplopia and proptosis. Imaging of the neuraxis showed marked bilateral trigeminal nerve hypertrophy and lumbosacral nerve root hypertrophy. Biopsy of the right infraorbital nerve revealed inflammatory infiltrates and extensive onion bulb formation, consistent with CIDP.

Adult↗
PubMed1996

Plasma-exchange therapy in chronic inflammatory demyelinating polyneuropathy. A double-blind, sham-controlled, cross-over study.

Eighteen patients with definite, untreated chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) of chronic progressive (nine patients) or relapsing course (nine patients) were randomized prospectively to receive 10 plasma-exchange (PE) or sham plasma-exchange (SPE) treatments over 4 weeks in a double-blind trial. After a wash-out period of 5 weeks or when they returned to baseline scores, patients were crossed over to the alternate treatments. Neurological function was assessed serially using a quantitative neurological disability score (NDS), a functional clinical grade (CG) and grip strength (GS) measurements. Electrophysiological studies were done at the beginning and end of each treatment. A primary 'intention to treat' analysis showed significant improvement with PE in all clinical outcome measures: NDS by 38 points, P < 0.001; CG by 1.6 points, P < 0.001; GS by +13 kg, P < 0.003 and in selected electrophysiological measurements, sigma proximal CMAP, P < 0.01; sigma motor conduction velocities, P < 0.006; sigma distal motor latencies, P < 0.01. Fifteen patients completed the trial and of those, 12 patients (80%) improved substantially with PE; i.e. five out of seven patients with chronic progressive course and seven out of eight patients with relapsing CIDP improved. There were three drop-outs; one patient lost venous access; one patient suffered a stroke and one patient left the trial to receive open treatment elsewhere. The improvement in motor functions correlated with the electrophysiological data, i.e. with improved motor conduction velocities and reversal of conduction block. Eight of 12 PE responders (66%) relapsed within 7-14 days after stopping PE. All improved with subsequent open label PE; all but two patients required long-term immunosuppressive drug therapy for stabilization. The PE non-responders improved with prednisone. We conclude that PE is a very effective adjuvant therapy for CIDP of both chronic progressive and relapsing course; concurrent immunosuppressive drug treatment is required. Exchange treatments should be given two to three times per week until improvement is established; the treatment frequency should then be tapered over several months.

Adolescent↗
PubMed1996

Varicella-zoster virus DNA in CSF and arteries in delayed contralateral hemiplegia: evidence for viral invasion of cerebral arteries.

A 78-year-old woman presented with a right basal ganglia infarct 6 weeks after a left herpes zoster ophthalmicus. MR angiography showed focal segmental stenosis of the proximal segments of the anterior, middle, and posterior cerebral arteries. Varicella DNA was detected in the CSF by polymerase chain reaction (PCR). Treated with dexamethasone and acyclovir without improvement, she died 1 month later. There was focal endarteritis in the left anterior, middle, and posterior cerebral arteries at autopsy. Varicella DNA was detected by PCR of extracts from these vessels but not from the arteries on the right side. This study provides further evidence that the vasculopathy after herpes zoster ophthalmicus results from direct viral invasion of the vessel wall.

Aged↗
PubMed1994

Expression of human immunodeficiency virus type 1 in the nervous system of transgenic mice leads to neurological disease.

Patients infected with the human immunodeficiency virus type 1 (HIV-1) frequently develop central and peripheral nervous system complications, some of which may reflect the effect of the virus itself. In order to elucidate the pathogenic mechanisms of HIV in neurological disease in a small animal model, we generated transgenic mice expressing the entire HIV genome under control of the promoter for the human neurofilament NF-L gene. The transgene was predominantly expressed in anterior thalamic and spinal motor neurons. Animals developed a neurological syndrome characterized by hypoactivity and weakness and by axonal degeneration in peripheral nerves. These results provide evidence for a role of HIV in affecting both the central and peripheral nervous systems. This animal model may also facilitate the development of therapeutic agents against the human disease.

Animals↗
PubMed1991

Type 2 fiber predominance in Lambert-Eaton myasthenic syndrome.

Serial muscle biopsies in a noncarcinomatous case of Lambert-Eaton myasthenic syndrome (LEMS) have shown progressive atrophy and loss of type 1 fibers, resulting in overwhelming type 2 predominance. A similar abnormality was found in a single biopsy from a second case of LEMS without associated carcinoma. Review of the literature suggests that type 2 fiber predominance has been observed in at least one other biopsied case. Interference with transmitter release caused by anti-voltage-gated calcium channel antibodies may deprive type 1 muscle fibers of the low frequency discharge necessary to maintain their metabolic properties.

Adolescent↗
PubMed1991

Chronic anemia in pregnant ewes: maternal and fetal effects.

To examine maternal and fetal responses to a sustained reduction in maternal hematocrit during days 110-138 of ovine gestation, 22 ewes and their singleton fetuses were instrumented. By repetitive exchange transfusions, the hematocrit in 12 ewes was decreased from 28.1 +/- 0.8 (baseline, day 110) to 14.0 +/- 0.7% (day 117) and maintained at that level. Anemic ewes demonstrated a transient increase in heart rate from 99 +/- 4 to 116 +/- 4 beats/min and a sustained increase in cardiac output from 117 +/- 8 to 153 +/- 11 ml.min-1.kg-1 compared with control animals. Uterine blood flow steadily increased in control animals from 868 +/- 100 (day 110) to 1,410 +/- 177 ml/min (day 138) but failed to increase in the anemic ewes. Uterine oxygen delivery fell from 83 +/- 10 to 39 +/- 4 ml/min with production of anemia and remained low in the anemic ewes. Arterial PO2 and oxygen content in the fetuses of anemic ewes fell transiently below control values (19.9 +/- 0.8 vs. 23.4 +/- 1.0 mmHg and 5.3 +/- 0.3 vs. 6.8 +/- 0.4 ml/dl, respectively) but did not persist. Fetal weights at 138 days gestation were lower in the anemic group (2,596 +/- 329 vs. 4,313 +/- 132 g). We conclude that chronic maternal anemia results in a decreased uterine blood flow as well as decreased uterine oxygen delivery. The fetus responds with decreased growth but does not develop sustained hypoxia or acidosis.

Anemia↗
PubMedDate not supplied

Herpes zoster vasculitis: demonstration by MR angiography.

A patient presented with multiple cerebral infarcts in various vascular territories after having been treated for herpes zoster ophthalmicus. Magnetic resonance angiography demonstrated multiple focal stenoses involving the proximal intracranial vessels which corresponded to endarteritis at autopsy.

Aged↗