Unilateral ankle dorsiflexor spasticity: an uncommon, disabling complication of transverse myelitis

Spasticity is a common complication after an upper motor neuron lesion and can involve a single or multiple muscle groups. When spasticity involves muscles around the foot, the typical pattern is ankle plantar flexed and inverted and toes flexed and adducted, giving rise to equinovarus deformity [1]. This pattern occurs due to the involvement of several muscles working in combination. Spasticity of the gastrocnemius, soleus and toe flexor muscles causes the ankle to plantarflex while the posterior tibialis muscle adds to the inward turn of the foot [2, 3]. Spasticity can also occur in a single muscle in the foot, for example spasticity of the extensor hallucis longus (EHL), also known as hitchhiker’s toe. This condition, albeit focal, occasionally causes pain and discomfort and is worth treating. However, spasticity involving a single muscle group such as the ankle dorsiflexors is rare and the complications are unknown. We report on a patient diagnosed with transverse myelitis presenting an unusual pattern of lower limb spasticity involving unilateral ankle dorsiflexor muscles. The spasticity resulted in foot deformity and difficulty wearing shoes, impairing gait, causing discomfort and generating disabili ties in activities of daily living (ADL). The patient is a 59-year-old woman diagnosed with transverse myelitis following symptoms of acute lower limb weakness and incontinent bladder and bowel. The patient’s initial clinical findings revealed flaccid tone and areflexia with Medical Research Council (MRC) grade 0/5 motor power in both of the lower limbs. Both upper limbs were intact neurologically. Pin prick sensation was impaired bilaterally from spinal level T8 downwards. Magnetic resonance imaging of the spinal cord disclosed a hyperintense area from the level of T9 vertebra to the conus medullaris. She was treated with 1 g of intravenous (IV) methylprednisolone for 5 days and three courses of intravenous immunoglobulin. The patient’s neurological impairments improved gradually after treatment. At 18 months, her right lower limb tone was normal with MRC grade 4/5 power. Her left lower limb tone was flaccid proximally. Distally, there was increased tone with ankle dorsiflexors showing Modified Ashworth Scale (MAS) grade 2 spasticity and toe extensors with MAS grade 3 spasticity (Figure 1). Her hip flexion had MRC grade 3/5, knee flexion and extension had MRC grade 2/5, whereas ankle dorsiflexion and plantarflexion had MRC grade 1/5. Pin prick sensation improved markedly with only impairment over bilateral lower legs remaining. Functionally, she was able to stand and walk therapeutically using a walking frame. The patient complained that her left foot and toes spontaneously hyperextended when she tried to move her left leg. This became more promiCorresponding author: Dr Mazlina Mazlan Department of Rehabilitation Medicine Faculty of Medicine 2nd Floor, Block R 50603 University Malaya Malaysia Phone: +6012-2069784 Fax: +603-79674766 E-mail: [email protected] Letter to the Editor