Dysfunction in macula, retinal pigment epithelium and post retinal pathway in acute organophosphorus poisoning

CONTEXT

Organophosphorus (OP) insecticide poisoning is a significant health problem in South Asian countries. Although cholinergic receptors are present at the junction between photoreceptors and the retinal pigment epithelium (RPE), human studies of the effects of OP poisoning on the visual pathways are very few. This study aims to demonstrate the pattern of changes in retina and post retinal pathways in patients with acute OP poisoning using visual electrophysiological tests.

METHODS

This is an observational, cross-sectional study conducted at the Neurophysiology Unit, Teaching Hospital, Peradeniya, Sri Lanka. We tested 16 patients recovered from cholinergic phase, at least 24 h after deatropinization and within 8 weeks of OP ingestion. We assessed the functional integrity of the photoreceptors and ganglion cells of the macula by pattern electroretinography (PERG); RPE by electro-oculography (EOG); and post retinal pathways by pattern reversal visual evoked potentials (PR-VEP). Latencies and amplitudes of PR-VEP and PERG, light peak (LP), dark trough (DT) and Arden ratio of EOG were determined in patients and compared with 16 controls using the Mann-Whitney U test.

RESULTS

Of the 16 OP-poisoned patients (median age of 37 ± IQR 20 years), six (37.5%) had reduced Arden ratio with reference to the International Society of Clinical Electrophysiology of Vision cut-off value of 1.7. The median Arden ratio in patients (1.69 ± IQR 0.36) was significantly lower compared to controls (1.90 ± IQR 0.4). The median latencies and amplitudes of PR-VEP or PERG were not significantly different between patients and controls. However, three patients had prolonged P100 latencies in PR-VEP and one had prolonged P50 latency in PERG.

CONCLUSIONS

Acute OP poisoning seems to affect the functions of the RPE and the visual electrophysiological changes outlast the cholinergic phase. Limited evidence suggests that photoreceptors of the macula region and post retinal pathway might be affected in some patients.

Acute neuromuscular paralysis, rhabdomyolysis and long lasting neurological deficits in Ceylon krait (Bungarus ceylonicus) bites: Two authentic cases from a serpentarium in Sri Lanka

The Ceylon krait (Bungarus ceylonicus) is a highly venomous elapid snake endemic to Sri Lanka. Its bites are rare and only seven reports are found in the literature. Therefore, the clinical manifestations and natural history of envenoming of Ceylon krait are not well studied yet. Neuroparalysis is the main clinical manifestation of their bites. We report two cases of proven Ceylon krait bites of two young snake keepers working in a serpentarium. They developed acute neuroparalysis, abdominal pain and a period of amnesia. The first patient developed myalgia and increased level of serum creatine kinase suggestive of rhabdomyolysis. One was treated with Indian polyvalent antivenom and both recovered with some long-lasting clinical disabilities namely impairment of sensation of the bitten arm and persistent refraction errors in the eyes in the first patient. The second patient had persistent marked nystagmus.

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Ceylon krait (Bungarus ceylonicus) is endemic to Sri Lanka and bites rarely.

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Two authentic bites are described.

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Both developed neuromuscular paralysis manageable without assisted ventilation.

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Long lasting deficits were sensory impairment of bitten arm, refraction errors and nystagmus.

An unusual case of hypothermia associated with therapeutic doses of olanzapine: a case report

Introduction

We report a case of a 42-year-old man who had symptomatic hypothermia as a result of taking olanzapine for paranoid schizophrenia. According to published data, only a few cases of hypothermia associated with olanzapine have been reported since its introduction into clinical use.

Case presentation

A 42-year-old Sri Lankan man with schizophrenia who was being treated with a therapeutic dose of olanzapine presented with reduced level of consciousness. He had a core temperature of 32°C and was bradycardic. At the time of admission, the electrocardiogram showed sinus bradycardia with J waves. He did not have any risk factors for developing hypothermia except the use of olanzapine. There was improvement in his clinical condition with reversal of electrocardiogram changes following gradual rewarming and the omission of olanzapine.

Conclusion

Hypothermia induced by antipsychotic medications is not uncommon, but olanzapine-induced hypothermia is rare and occurrence has been reported during initiation or increasing the dose. But here the patient developed hypothermia without dose adjustment.