Description

A teenage girl was admitted to the emergency department with sudden-onset vomiting, abdominal pain and dizziness. Her relatives provided a history of rat poison (rodenticide) intake (approximately half packet, the full packet contains 10 g of zinc phosphide (Zn₃P₂); therefore, we estimated that she had ingested approximately 5g a few hours earlier. Immediately after routine basic investigations and stabilisation, gastric lavage was performed. On physical examination, her vital signs were normal, except for tachycardia (pulse rate 130 beats/min). She was able to follow one-step commands. Deep tendon reflexes were vigorous with bilateral extensor plantar responses. Extraocular movements were regular without nystagmus. After 2 days of hospitalisation, she began to exhibit behavioural changes, worsening confusion and disorientation, and over the next few hours, her condition rapidly deteriorated. With these features in mind, central nervous system (CNS) involvement was suspected, and a MRI scan of the brain was performed, which revealed symmetrically distributed diffusion restriction in bilateral periventricular supratentorial white matter with a reversal in apparent diffusion coefficient images. The sulcal spaces were effaced in bilateral cerebral hemispheres signifying brain oedema. However, the remaining MRI sequences (T1, T2, fluid attenuated inversion recovery and susceptibility weighted images) did not reveal any abnormality (figure 1A–D). This white matter diffusion restriction without any abnormality on other MRI sequences has many differentials like toxic leucoencephalopathy, cranial irradiation, chemotherapy, immunosuppressive therapy, antimicrobial medications (eg, metronidazole), environmental toxins and drug abuse. Based on the history and MRI features, a diagnosis of leucoencephalopathy secondary to chemical rodenticide ingestion was made. As there is no specific antidote, the patient was managed conservatively. After a few days, her neurological symptoms gradually resolved, and she was able to perform her daily activities independently (table 1). After 3 weeks, a follow-up MRI brain scan showed complete normalisation of MRI abnormalities, and (figure 2A–D) she remains under follow up.

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Figure 1

MRI of the brain in the axial plane. (A, B) Restricted diffusion in bilateral periventricular supratentorial white matter (white star) with reversal in corresponding apparent diffusion coefficient images. (C) T1 weighted and (D) FLAIR images do not show any abnormality in the same regions except the effacement of sulci and gyri due to diffuse brain oedema (white star). (These images have been made by the author)

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Figure 2

Follow-up MRI brain of the same patient, axial plane. (A) Diffusion image; (B) Apparent diffusion coefficient (ADC) image; (C) T1-weighted image; (D) FLAIR image shows no abnormality in bilateral periventricular supratentorial white matter. The cerebral oedema is also subsided (white stars). (These images have been made by the author)

Rodenticides comprise various types of agents with different toxicity profiles. Phosphides such as aluminium phosphide and Zn₃P₂ are among the most commonly used in India. When ingested, these phosphides react with gastric acid and form phosphine gas, which is highly lethal.1 As these rodenticides are cheap and readily available on the market, ingestion (as a suicide agent) has become a public health problem, especially in rural areas.2 Although clinical and laboratory properties of metal phosphide poisoning have been described in the literature, very few clinical-radiological correlations of such cases have been published. Radiographic findings pertaining to pulmonary and abdominal complications have been described in previous reports of Zn₃P₂ poisoning.3 In our opinion, awareness of these MRI features would help emergency physicians or toxicologists/radiologists to detect this complication early and plan the appropriate treatment. To evaluate the CNS complications, MRI is the choice of investigation as it can be used to differentiate various types of leucoencephalopathy. It was found that this type of leucoencephalopathy can be treated symptomatically and is usually resolves with time. Here, we have described typical CNS imaging features in a patient with Zn₃P₂ poisoning, which, as far as we know, has not been reported in the literature.