Ultrasonic evidence of mononeuritis multiplex caused by Lyme neuroborreliosis

European Lyme neuroborreliosis (LNB) typically presents with facial palsy or a triad of painful radiculitis, peripheral motor deficits, and lymphocytic inflammation of the cerebrospinal fluid (Bannwarth syndrome). We describe a patient with an atypical presentation in whom ultrasound aided in the diagnosis. A 58-y-old woman presented with a 7 wk history of progressive numbness and pain on the plantar surface of her right foot and increasing trouble walking. Symptoms began with numbness of her fourth and fifth toes and soreness of the bottom of her foot. Weeks later, similar symptoms began beneath her first to third toes and then her ankle. On admission, she had no back or radicular pain and had no recollection of tick bites or skin lesions. A lumbar MRI done 2 wk earlier was normal. On examination, she had severe plantar hypoesthesia with allodynia and slight weakness of toe flexion with normal toe extension and normal ankle plantar and dorsiflexion on the right. She was tender to palpation behind her right medial malleolus and had a positive Tinel's sign. Tendon reflexes, blood count, C-reactive protein (CRP), electrolytes, liver, thyroid, and renal function tests were normal. Two days later her foot became edematous with reddish skin changes, and tarsal tunnel syndrome with complex regional pain syndrome was suspected. A trial of 50 mg per day of prednisone was started with improvement in pain and edema. However, 6 days later, hypoesthesia, allodynia, and pain progressed to involve her lower leg in a stocking distribution, and she developed a Medical Research Council (MRC) scale grade 4 for toe extension and of ankle plantar and dorsiflexion. Nerve conduction studies (NCS) showed signs of severe axonal loss in the right tibial, peroneal, and sural nerves (Table 1). Needle electromyography of the peroneus longus muscle showed fibrillation potentials and positive sharp waves associated with reduced recruitment. Ultrasound (GE, P9, 15 MHz linear multiplanar probe) of her right sciatic, peroneal, and tibial nerves at the popliteal fossa and of the sural and tibial nerves at the ankle showed enlarged cross-sectional area (CSA) values compared to her normal left side and published reference values (Figure 1A–J) and diffuse thickening of nerve fascicles (Figure 1K, L). Additionally, the tibial nerve showed hyperechogenicity of the epineurium and intraneural soft tissue at the popliteal fossa and the medial malleolus (Figure 1M, N), suggesting nerve inflammation. A lumbar puncture done immediately after electrophysiological and ultrasound exams revealed 244 cells/mm and protein of 120 mg/dL. Intravenous ceftriaxone 4 g/day was started immediately. Two days later, neuroborreliosis was confirmed with a positive intrathecal immunoglobulin IgM and IgG index of 11.15 and 39.45 respectively. Cerebrospinal fluid tests for syphilis and varicella zoster virus were negative. At that time, the dose of ceftriaxone was lowered to 2 g/day for 2 days followed by oral doxycycline 100 mg twice daily for 14 days. The patient experienced reduced pain and normalization of muscle strength over 4 wk. Tolerable neuropathic pain remained 1 y after treatment. An MRI of her right ankle showed right tibial nerve enlargement with contrast enhancement.