A Rare Cause of Bilateral Wrist Drop.

Sir,

We report a case of a 27 year old male patient who had come with bilateral wrist drop. Patient had difficulty in extending the left wrist for 6 months which progressed to involve right wrist for last 2 months [Figure 1]. He did not have any numbness or paraesthesia. There was no significant past medical or family history. He had been working in a battery manufacturing factory for last 4 years. On physical examination, he had mild pallor. Neurological examination revealed weakness of wrist extensors without any sensory loss. Weakness was asymmetric, being more in the left wrist (Medical Research Council grade 2 power) compared to the right (MRC grade 4). Wrist flexors were spared. Rest of the neurological examination including cognitive and neuropsychological testing was unremarkable. On routine laboratory investigations, he was found to have hemoglobin of 10.8 gm/dl with microcytic hypochromic red cells without any basophilic stippling. Serum iron profile was normal. Liver, renal, and thyroid function tests were normal. Glycemic profile was normal. Human immunodeficiency virus testing by enzyme-linked immunosorbent assay was negative. Anti-nuclear antibody testing by indirect immunofluorescence assay was also negative. Electrophysiological studies did not show any motor response on bilateral radial nerve stimulation with reduced compound muscle action potential amplitude in left median nerve [Figure 2]. In view of asymmetric motor weakness involving bilateral upper limbs with history of exposure to lead plates at work place, lead neuropathy was suspected. Blood lead levels were found to be high (52.6 mcg/dl; acceptable range upto 10 mcg/dl). Patient was started on oral penicillamine. He was educated regarding his illness to prevent further intoxication. The factory officials were told to ensure safety control measures at work place. Later he was discharged to follow-up in outpatient department.

Figure 1

Patient with bilateral wrist drop

Figure 2

Electrophysiological images showing non recordable motor response in bilateral radial nerves

Lead (Pb) is used in many industries, such as construction, ceramics, paints, and storage battery manufacturing. It is a common occupational hazard. It is used in various forms because of its properties including ease of casting and fabrication, resistance to corrosion, and a low melting point.[1] It enters the body through respiratory, gastrointestinal or cutaneous absorption.The common sources of lead poisoning are fumes from burnt car batteries, and ingestion of flaking paint.[2] Due to its prolonged elimination half-life, it accumulates in the body over time. It is excreted out of the body mainly through renal and gastrointestinal route.

Lead may affect both central and peripheral nervous systems. It can range from mild confusion and lethargy to refractory seizures and severe encephalopathy. Central nervous system involvement is more common in children as compared with adults due to the occurrence of pica.[3] Chronic exposure to Pb may cause neuropsychiatric symptoms and mild cognitive impairment.[3]

Lead intoxication can lead to two forms of neuromuscular syndromes: a subacute predominantly motor syndrome and a chronic sensory and autonomic syndrome. It causes predominantly motor, but rarely sensory neuropathy. The weakness is more common in the upper limbs than in the lower limbs. Usual clinical presentation is a unilateral wrist drop. Our patient had bilateral wrist drop following chronic exposure to lead at workplace. Similar weakness in lower limbs, causing a “foot drop,” may be seen in children.[3] Extensive safety control measures should be imposed at the workplace to prevent such occupational hazards.

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