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Acute disseminated encephalomyelitis following snake bite in a child: A rare complication
Rakesh Ramanan, Shaji Velayudhan Cheruvallil, Kabeer Abdulkhayarkutty, Prasanth Sudhakaran
Department of Neurology, Government TD Medical College, Alappuzha, Kerala, India
|Date of Submission||27-Sep-2020|
|Date of Decision||04-Dec-2020|
|Date of Acceptance||29-Dec-2020|
|Date of Web Publication||19-Jul-2021|
Department of Neurology, Government TD Medical College, Alappuzha, Kerala.
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Acute disseminated encephalomyelitis (ADEM) occurs in children commonly following infections and vaccination. Central demyelinating disorder such as ADEM following snake bite is rarely reported. We present a case of an 11-year-old boy who developed altered sensorium and quadriparesis suggestive of ADEM following a cobra bite. The role of early diagnosis with a high index of clinical suspicion and optimum neuroimaging modality in recovery is highlighted.
Keywords: ADEM, snake bite
| Introduction|| |
Worldwide around 4.5 to 5.4 million people a year are bitten by snakes, and the death toll could range from 81,000 to 138,000 per year. In India alone, it has been estimated that around 2.8 million people are bitten by snakes, and 46,900 people die from snakebite every year, more than 25% of them children less than 15 years. The common poisonous snakes seen in India are Indian cobra, krait, Russel’s viper, and saw- scaled viper. ADEM, a central demyelinating disorder, can occur as a rare complication following a snake bite. ADEM following a cobra bite is rarely reported in children. We present a case of ADEM in a child after a treated cobra bite.
| Case History|| |
An 11-year-old boy, born out of a non-consanguinous marriage, developmentally normal, immunized for age, was brought to the casualty after being bitten by a cobra on his left ankle while playing in a paddy field. He had severe pain but continued to play for another half an hour following which he fell unconscious and was taken to our hospital. At admission, the child was comatose, Glasgow Coma Scale score of three, sluggishly reacting pupils, severe respiratory distress with oxygen saturation of 65% on room air, with feeble peripheral pulses, bradycardia, and systolic blood pressure of 70mm Hg. The child was immediately intubated and ventilated, was administered 10 vials of polyvalent anti-snake venom (ASV). The child was started on broad-spectrum antibiotics, inotropic support, intravenous fluids, and injection neostigmine. His Whole blood Clotting Time was within normal limits. Renal and liver function tests were normal.
The patient recovered gradually and was extubated after 48 hrs. The child had normal sensorium and no evidence of any focal neurological deficits after extubation. On day 4 the child developed left focal seizures lasting 5 mins followed by a deterioration in sensorium. Physical examination at this stage showed a restless and irritable mentation with bilateral ptosis, restriction of upgaze, generalized hypotonia, and flaccid quadriparesis (Grade 2/5 in the upper limbs and grade 3/5 in lower limbs). There was generalized areflexia and plantar reflex was bilaterally extensor.
In view of newly developed neurological deficits and worsened sensorium, ADEM was considered as a possibility and Magnetic Resonance Imaging (MRI) brain was done, which showed T2 FLAIR (Fluid Attenuated Inversion Recovery) hyperintense signals in the bilateral frontal and parietal cortex and basal ganglia [Figure 1] and [Figure 2] suggestive of ADEM. The nerve conduction study did not reveal any evidence of peripheral demyelination. Though the need for lumbar puncture and the cerebrospinal fluid study was explained in detail, parents did not consent for the same. The child was started on injection Methylprednisolone, and after 2 days of treatment limb power and sensorium of the child started improving. Within 5 days of treatment, he improved markedly except for a persistent bilateral upper limb distal weakness in the form of bilateral wrist drop. He was placed on physical rehabilitation therapy and was discharged on day 10 on oral steroids, which was tapered and stopped by 3 weeks. At follow up he had minimal distal weakness of his upper limbs and mild spasticity of both lower limbs.
|Figure 1: MRI brain FLAIR sequences showing hyperintense signals in A bilateral basal ganglia and B bilateral frontal and parietal cortex|
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|Figure 2: MRI brain A Diffusion weighted and B apparent diffusion coefficient sequences showing hyperintense signals (T2 shine through) in bilateral basal ganglia, frontal and parietal cortex|
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| Discussion|| |
ADEM is a central demyelinating disorder characterized by multifocal neurological dysfunction that often occurs in association with immunization or vaccination or systemic viral infection. It usually presents as a monophasic illness with the characteristic clinico-radiological picture of multifocal demyelination. There are reported cases of peripheral nervous system demyelination following a snake bite causing Guillain-Barre syndrome and delayed polyneuropathy., However central demyelinating disease such as ADEM is rare following a snake bite. Demyelination following snake bite could be due to similarities between components of snake venom and myelin which lead to the generation of pathogenetic antibodies causing destruction of the myelin.
The neurological consequences of neurotoxic snake bite are due to the inhibition of transmission at the neuromuscular junction, which can lead to respiratory paralysis.
As such, hypoxic-ischemic encephalopathy could qualify as a differential diagnosis in this case. However, the fact that the child had completely recovered from the initial insult and subsequently developed fresh neurological deficits, rules it out. Radiological findings according to diagnostic criteria by Krupp et al. for pediatric ADEM require that brain MRI should be abnormal during the acute (three months) phase with typical features: a) Diffuse, poorly demarcated, large (>1–2cm) lesions involving predominantly the cerebral white matter, b) T1 hypointense lesions in the white matter are rare, c) Deep grey matter lesions (thalamus or basal ganglia) can be present. According to this, the radiological picture in our case was evidently suggestive of ADEM.
High-dose intravenous methylprednisolone (30mg/kg/day for 5 days) is currently widely accepted as first-line therapy in ADEM. Good functional recovery has been reported in about 60–85% of cases following steroid therapy., Our patient responded to high dose steroid therapy. Intravenous immunoglobulin (IVIG) and Plasma exchange are second-line treatment options, helpful in steroid-unresponsive ADEM and in patients who have contraindications to corticosteroids. These are successful in 40–50% of steroid-resistant patients.
| Conclusion|| |
ADEM can rarely occur as a complication following a snake bite. Early improvement followed by fresh onset multifocal neurological dysfunction, clinches the diagnosis. High index of clinical suspicion and optimum neuroimaging study (MRI brain) aids in early institution of effective treatment and rehabilitation.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]