Tibial Neuropathy Associated with Behcet's Disease

Abstract

A 39-yr-old female patient was admitted to the neurology department reporting a burning pain and a tingling sensation on the left sole, which was followed by weakness of the left toes for >2 wks. Two years previously, she had experienced similar symptoms on the right sole, which improved with conservative management. On admission, recurrent oral ulcers, genital ulcers, and a uveitis history were identified, which met the diagnostic criteria of Behcet's disease (BD).1 A neurologic examination showed slight weakness in flexion, extension, and abduction of the left toes (Medical Research Council grade IV), and a sensory examination revealed hypoesthesia on the left sole and on the anterior one third of the right sole. Deep tendon reflexes were normoactive, no pathologic reflexes were observed, and Tinel's sign was positive at the left medial malleolus. Nerve conduction studies revealed decreased amplitude of the compound motor action potentials and no F-waves in either tibial nerves. Needle electrode examination revealed positive sharp waves in muscles innervated by the left tibial nerve and large amplitude polyphasic motor unit potentials in bilateral tibial nerve innervated muscles. Ankle magnetic resonance imaging (MRI) 2 wks after symptom onset revealed diffuse swelling with heterogeneous enhancement in the left tibial nerve at the calf level and high signal intensities in the left flexor hallucis longus, flexor digitorum longus, and tibialis posterior muscles. (Figs. 1A, B) There was no evidence of a structural lesion compressing the tibial nerve. Lower extremity MRI at thigh level revealed no signal change in the sciatic nerve or surrounding muscles, and lumbar spine MRI showed no evidence of root compression. Her sensory symptoms improved significantly after administering intravenous steroid (1000 mg methylprednisolone) for 5 days.FIGURE 1: Sagittal fat-suppressed fast T2-weighted (A) and fat-suppressed gadolinium-enhanced T1-weighted spin-echo magnetic resonance images (B) show diffuse swelling and heterogeneous enhancement of the left tibial nerve (arrows) at the calf level.Although the central nervous system is frequently involved in BD, peripheral nervous system involvement has rarely been described.2,3 However, recent studies have revealed that subclinical involvement of the peripheral nervous system is not uncommon in BD, and, thus, associations between BD and peripheral nervous system dysfunction are to be expected.4 In our case, recurrent tibial neuropathy was suspected, and no other specific cause except BD for tibial neuropathy was found. Our case suggests that recurrent mononeuropathy is a possible presenting symptom of BD, and that BD should be considered in patients with idiopathic recurrent mononeuropathy.