Focal neuromyotonia as a presenting feature of lumbosacral radiculopathy
A 36-year-old man presented with back pain and cramp like pain in both lower limbs of 4 month duration. Pain was initially dull aching localized to the lower back, aggravate on walking and partially subside with rest and analgesics. Simultaneously, he developed cramp like pain in both calves along with stiffness, which he initially noticed while walking. Initially, he had to take pauses while walking. Later on, there was severe difficulty in walking. Since, 2 months, patient developed severe cramp like pain even at rest, affecting his sleep. Along with the muscle cramps, he noticed formation of a transient lumps in both calves due to focal muscular contraction. He did not complain of any radicular pain, tingling, numbness or any other sensory complaints. There was no excessive sweating. He noticed twitching in both calves since 2 months. There was no history of any weakness or thinning noticed in lower limbs. He did not have any complaints in upper limbs. Family history was not significant. His general examination was unremarkable. Higher mental functions and cranial nerves were normal. Upper limb examination was normal. Lower limb examination revealed mild thinning in the left leg. There was frequent rippling noted in both calves. Tone, power, and reflexes were normal. There was no sensory loss, but because of pain and cramps he had severe limitation of walking. Spine examination revealed tenderness and spasm in lower paraspinal muscles. There was no deformity. Straight leg-raising testing was positive on both sides. There was no evidence of autonomic involvement.\nHematological and biochemical tests including blood sugar, kidney function tests, serum electrolytes including calcium, thyroid profile were normal. Nerve conduction study revealed mildly reduced tibial compound muscle action potential amplitude with normal sural sensory nerve action potential. Electromyography (EMG) in bilateral gastronomies lateral head revealed spontaneous activity in the form of doublets, triplets and neuromyotonic discharges (160-200 Hz waning type of discharges with pinging sound). There was reduced recruitment, incomplete interference pattern along with polyphasic motor unit potentials (MUP) in bilateral L5, S1 innervated muscles (Tibialis anterior and hamstrings). Lumbar paraspinal EMG revealed fibrillation potentials. Bilateral H reflex testing didn’t show any recordable waveforms []. EMG in both quadriceps muscles was normal. Magnetic resonance imaging Lumbosacral spine revealed annular tear along with disc protrusion at L3-4, L4-5 with severe foraminal (right > left) and spinal canal stenosis along with compression of the nerve roots. There was contrast enhancement noted in the protruded disc and nerve roots suggestive of active inflammation []. Patient received intravenous methylprednisolone for 3 days, carbamazepine 200 mg twice a day, duloxetine 20 mg once a day and physiotherapy. There was marked relief in pain, stiffness and cramps after 10 days. Even the calf muscle rippling was drastically reduced.