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Biomedical subjects

J G McLeod

Publications and source records attributed to J G McLeod.

At least 19 recordsLinked to original sources

Invited review: autonomic dysfunction in peripheral nerve disease.

The autonomic nervous system is affected in most peripheral neuropathies, but only in a small number of conditions, such as diabetes, amyloidosis, Guillain-Barré syndrome, porphyria, and familiar dysautonomia, is autonomic dysfunction of clinical importance. The pathological changes in the peripheral autonomic nervous system are similar to those in the peripheral somatic nerves. Autonomic disturbances are most likely to occur when there is acute demyelination or damage to small myelinated and unmyelinated fibers. Autonomic investigations should include tests of both sympathetic and parasympathetic function. Treatment consists of management of the underlying cause of peripheral neuropathy, physical and pharmacological measures.

Animals

Autonomic dysfunction in peripheral nerve disorders.

The autonomic nervous system is affected by most conditions that cause peripheral neuropathy. Autonomic dysfunction may be clinically significant in some conditions such as diabetes, amyloidosis, Guillain-Barré syndrome and porphyria, but in many the autonomic disturbances are of only minor clinical importance. Clinical tests of both sympathetic and parasympathetic function are necessary to establish the diagnosis.

Autonomic Nervous System

Autonomic function in hereditary motor and sensory neuropathy (Charcot-Marie-Tooth disease)

Autonomic tests of heart rate and blood pressure control using both invasive and noninvasive techniques were performed on 11 patients with hereditary motor and sensory neuropathy (HMSN) types 1, and 4 patients with HMSN type 2. The results were compared with those of 76 control subjects. No significant difference was found between the patient and control groups. Impairment of sweating on the extremities was found in patients with HMSN types 1 and 2, consistent with distal degeneration of sympathetic fibers in peripheral nerves, but there were no abnormalities of cardiovascular reflex control mechanisms.

Adolescent

Vasculitic neuropathy. A clinical and pathological study.

The clinical, electrophysiological and pathological features and prognosis of 34 patients with peripheral neuropathy caused by necrotizing vasculitis were evaluated. The causes included polyarteritis nodosa and its Churg-Strauss variant, rheumatoid arthritis, undifferentiated connective tissue disease, Wegener's granulomatosis, primary Sjögren's disease, and chronic lymphocytic leukaemia with cryoglobulinaemia; 2 patients had no evidence of systemic vasculitis. Mononeuritis multiplex was the most common clinical manifestation, followed by asymmetrical polyneuropathy and distal symmetrical polyneuropathy. Pain was a frequent symptom. Nerve conduction studies were abnormal in all cases, and in 3 patients there was conduction block or severe slowing of motor conduction. Necrotizing vasculitis was present in sural nerve biopsies of most cases, and severe active axonal degeneration was a dominant feature. Immunofluorescent staining of blood vessels for immunoglobulin, C3 and fibrinogen was positive in all cases in which it was performed, even when there was no cellular infiltration. All patients were treated with prednisone alone or in combination with other immunosuppressive agents, or with plasmapheresis. Long-term follow-up studies demonstrated that although the peripheral neuropathy usually improved and caused only mild to moderate functional disability, the long-term prognosis of the systemic disease was poor with a 5-yr survival of only 37%.

Adult

Autonomic function in Friedreich's ataxia.

Autonomic function studies were performed on 15 patients with Friedreich's ataxia, and the results compared with those of 76 healthy subjects. There was an increase in resting supine heart rate, attributed to cardiac abnormalities. Other tests of sympathetic and parasympathetic function were normal. The normal autonomic function studies are consistent with the pathological findings of degeneration predominantly of large diameter myelinated fibres with sparing of small myelinated and unmyelinated fibres.

Adolescent

Superior sagittal sinus thrombosis.

Seven cases of superior sagittal sinus thrombosis seen at Royal Prince Alfred Hospital over the 10 year period 1979 to 1989 have been reviewed. Diagnosis was confirmed by angiography, CT scan or autopsy. The average age was 33 years (16 to 47 years). Five of the patients were female and 2 male. On CT scan the 'empty delta' sign, present in 4 cases, was the most specific diagnostic feature. The underlying causes included primary thrombocythaemia, homocystinuria, post-angiographic investigation of an arteriovenous malformation, and oral contraceptives. In 2 cases no cause was found. Headache was the commonest and earliest symptom, being followed in frequency by convulsions and hemiparesis. Hemiparesis was the commonest sign observed, followed by papilloedema, cranial nerve palsies and impaired level of consciousness. Five of the patients developed signs and symptoms of raised intracranial pressure prior to the appearance of focal neurological deficits, mostly likely due to propagation of the thrombosis to cortical veins. There have been no controlled trials of therapy; however it is important to treat raised intracranial pressure rapidly and effectively, and although the role of anticoagulants remains controversial, their early use may be indicated when there is no radiological evidence of haemorrhage.

Adolescent

Anosmia after doxycycline use.

We report the case of a man who developed anosmia while taking doxycycline tablets for a skin disorder. Two other cases of parosmia occurring in association with doxycycline have been reported to the Adverse Drug Reactions Advisory Committee of the Commonwealth Department of Community Services and Health since 1972. Disturbances of taste but not olfaction have been reported with tetracycline use in the past.

Acne Vulgaris

Magnetic resonance imaging in clinically-definite multiple sclerosis.

Forty-two patients with clinically-definite multiple sclerosis were examined by magnetic resonance imaging using a 1.5-T instrument. Magnetic resonance imaging detected an abnormality in 90% of patients. In four patients, no lesions were demonstrated. The number, size and site of the lesions by magnetic resonance imaging were compared with the patients' clinical status and other variables. The Kurtzke disability status scale score increased in patients with corpus callosum atrophy, and brainstem and basal ganglia lesions, and correlated with the total number of lesions. No correlation was shown between the findings of magnetic resonance imaging and disease duration, age, sex or pattern-reversal visual-evoked potentials. This article highlights the variety of magnetic resonance images that is obtained in patients with clinically-definite multiple sclerosis.

Adult

Autonomic function and unmyelinated fibers in chronic inflammatory demyelinating polyradiculoneuropathy.

Because autonomic function may be abnormal in some demyelinating peripheral neuropathies, it has been studied with a number of noninvasive and invasive tests in 14 patients with chronic inflammatory demyelinating polyradiculoneuropathy. There were abnormalities of the 30:15 ratio in 3 patients and an abnormal thermoregulatory sweat test in 5 patients. These findings are indicative of mild parasympathetic and sympathetic dysfunction. Minor pathological changes in unmyelinated fibers were demonstrated on morphometric examination of sural nerves of 10 patients.

Adolescent

Effect of neural activity on skeletal muscle phosphoproteins.

A number of phosphoproteins were found in the soluble fraction of rat skeletal muscle by two-dimensional polyacrylamide gel electrophoresis (PAGE). The pattern of some of these phosphoproteins differed in fast (extensor digitorum longus, EDL) or slow (soleus) muscles, was dependent on normal innervation, and was altered with denervation. In order to determine if the pattern was maintained by electrical activity or trophic factors, we compared the effect of electrical block by local neural application of tetrodotoxin with the effect of complete nerve section. Both methods produced similar alterations in phosphoproteins, indicating that the pattern is dependent on nerve activity, not trophic factors. Such phosphoproteins are possible mediators of neural activity on gene expression.

Animals

The effect of ageing on autonomic nervous system function.

We studied 76 healthy subjects (five-85 years) with a number of invasive and non-invasive tests of autonomic function. Age related effects were found with the tests of predominantly vagal cardiovascular function. However, there were no age related effects found with the tests of predominantly sympathetic cardiovascular function. The age of the subject should be taken into consideration when evaluating tests of autonomic function and each laboratory should establish its own control values.

Adolescent

Multiple sclerosis in Australia and New Zealand: are the determinants genetic or environmental?

The prevalence of multiple sclerosis (MS) has been recently reported from nine regions of Australia and New Zealand. There is a marked variation of prevalence with latitude. MS is seven times more common in southern New Zealand than in tropical Queensland. On current evidence, it is suggested that in both countries this variation is predominantly due to environmental rather than genetic factors.

Australia

HLA antigens in chronic inflammatory demyelinating polyneuropathy.

HLA typing of 71 patients with chronic inflammatory demyelinating polyneuropathy (CIDP) showed an overall increase in frequencies of HLA-A3, -B7, -DR2 as well as concomitantly decreased frequencies of HLA-44 and DR7. The strongest associations were seen with HLA-DR2, -DR7 and -B44 in CIDP overall, although they did not reach statistical significance.

Chronic Disease

Cyclosporin A in the treatment of chronic demyelinating polyradiculoneuropathy.

Eight patients with chronic inflammatory demyelinating polyneuropathy, five of whom had an associated paraproteinaemia, were treated with cyclosporin in a pilot, uncontrolled study for periods up to three and a half years after failing to respond adequately to corticosteroid and azathioprine therapy and plasmapheresis. Three patients had an excellent response, two with complete remission. In other cases it was possible to reduce the corticosteroid therapy and frequency of plasmapheresis. There were no serious complications of the treatment.

Adrenal Cortex Hormones

Cranial magnetic resonance imaging in chronic demyelinating polyneuropathy.

Twenty one patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and five patients with chronic demyelinating polyneuropathy associated with benign monoclonal paraproteinaemia none of whom had signs or symptoms of central nervous system disease, had cranial magnetic resonance imaging (MRI) on a 1.5 Tesla unit. Areas of increased white matter signal intensity were seen in one of 10 patients aged less than 50 years and in five of 16 patients aged more than 50 years. In only two of the patients (8%), neither of whom had paraproteinaemia, did the appearance strongly suggest demyelination. The only clinical variable that predicted MRI changes was age (p less than 0.01).

Adult

Abnormal cough reflex in canine acrylamide neuropathy.

Coughing in response to irritation of the airways is a fundamental protective reflex that is dependent on rapidly adapting bronchopulmonary receptors and their vagal afferent fibers; reflex airway constriction, which is effected by vagomotor efferent fibers, usually accompanies coughing. Although dysfunction of vagally mediated cardiovascular and gastrointestinal reflexes is a well-documented complication of autonomic neuropathy, to date there have been no studies of the effect of peripheral autonomic failure on the cough reflex. In the study reported here, we examined the effect of acrylamide-induced neuropathy, a distal axonopathy, on the ventilatory and tracheomotor components of the cough reflex in conscious dogs. There was a reduction in the cough reflex in response to mechanical irritation of the large airways in the preclinical phase of the neuropathy, and the cough reflex was virtually abolished when the dogs had moderate neuropathy. Following withdrawal of the neurotoxin, there was a substantial recovery of the cough reflex in surviving animals. It is possible that the cough reflex may be reduced in patients with vagal neuropathy and that this might compromise protection of the airway.

Acrylamide