Inverted V sign in hydromyelia with Chiari type 1 malformation

Abstract

A 21-year-old man presented with 7 months of progressive numbness in both dorsal hands. Examination showed bilateral pinprick sensory loss over the dorsum of the hands, loss of vibration and joint position sense in the fingers, and bilateral Tromner signs. Muscle strength and deep tendon reflexes were normal. Magnetic resonance imaging (MRI) showed inferiorly displaced cerebellar tonsils suggestive of Chiari type 1 malformation (Fig. 1a) and hydromyelia from the level of C2–T4 (Fig. 1b, c) [1]. Transverse T2-weighted MRI demonstrated an enlarged central canal and an inverted V shaped T2-hyperintensity starting on both sides of the central canal and extending into posterior gray and white columns (Fig. 2). It seemed that the intensity of this signal changes was different from the intensity of the central canal itself. Inverted V sign refers to inverted V shaped bilateral symmetric hyperintensity within the posterior columns on axial T2-weighted MRI and is classically described in subacute combined degeneration of the spinal cord [2]. But the patient’s vitamin B12 level was normal (671 pg/mL; normal 211–946 pg/mL). A recent study has reported parenchymal changes of the posterior white and gray columns in syringomyelia associated with Chiari type 1 malformation [3, 4]. It is believed to be related mainly to the extracellular fluid accumulation due to disturbed absorption mechanisms [3, 4]. Therefore, in our case, inverted V sign may be due to Chiari type 1 malformation rather than subacute combined degeneration. Hence, a final diagnosis was made of hydromyelia with Chiari type 1 malformation and the patient was offered foramen magnum decompression. Our case suggests that inverted V sign is diagnostically helpful, but not specific to subacute combined degeneration of the spinal cord. And, hydromyelia with Chiari type 1 malformation should be considered in the differential diagnosis of conditions in which inverted V sign can be found.