Chiari i malformation presenting as unilateral toe walking in a 17-month-old.

Abstract

Toe walking is a common developmental occurrence in young children and is most often benign and self-limiting. However, it can be a presenting sign of an underlying disorder such as cerebral palsy, myopathy, neuropathy, spinal dysraphism, a tight Achilles tendon or autism spectrum disorder.1 Chiari I malformation is a rare cause of toe walking and foot drop, and few cases have been reported in the literature.2 The patients on whom the published cases were based ranged in age between 43 and 164 years; however, we report the case of a boy who presented with unilateral toe walking due to Chiari I malformation and holocord syringomyelia at just 17 months. Our patient is a second twin, born at 34 weeks of gestation weighing 2.51 kg, following a pregnancy complicated with maternal cholestasis and hypertension. He experienced mild hyaline membrane disease requiring respiratory support, mild hypoglycaemia and jaundice. He sat, crawled and walked at 6, 8 and 16 months, respectively, presenting to a paediatric clinic in regional New South Wales with left-sided toe walking at 17 months. The other developmental domains were age appropriate. The patient's mother had a fusion of the fifth and sixth cervical vertebrae. The first twin had an unremarkable developmental history. On examination, he walked high up on his left foot. There was significantly increased tone at the left Achilles tendon and the foot rolled slightly into an equinovarus position. The right ankle was normal. The tone and reflexes at the knees were normal bilaterally. The rest of the examination was unremarkable. The toe walking seen in this case differed from that which is benign and self-limiting for several reasons: it was unilateral, persisted for a significant period and the presence of neurological signs including abnormal foot position and increased tone. Further evaluation revealed normal haematology, liver and renal functions and creatinine kinase. Plain radiographs of the back and hips were normal. The magnetic resonance imaging (MRI) brain showed the cerebellar tonsils descending 10 mm into the crowded foramen magnum, consistent with a Chiari I malformation. The T2 MRI spine showed a hydrosyringomyelia (syrinx) extending from C2 to spinal cord termination in the mid-body of L1 (Fig. 1). Its widest point was 3 mm in diameter in the mid-thoracic spine and there was no cord compression. At 22 months, he underwent posterior cranial fossa decompression at a tertiary children's hospital. Remarkable improvement in the toe walking was seen just weeks post decompression. He was noted to have a normal heel to toe gait and could achieve dorsiflexion of 20° when squatting on the ground. A follow-up MRI showed a thin syrinx and the Chiari decompression remained, with cerebrospinal fluid around the foramen magnum. His gait remained normal at 5 years of age. An MRI is indicated only when a detailed neurological examination uncovers neurological abnormalities. Our case highlights the importance of carefully evaluating unilateral toe walking as this is one possible presentation of Chiari I malformation, which is a surgically correctable cause of toe walking. Written consent was obtained from the patient's parents.