Hypertrophic Olivary Degeneration-DTI

Hypertrophic olivary degeneration (HOD) is usually caused by a lesion in the triangle of Guillain and Mollaret and presents clinically as palatal tremor. This case is a young lady with known lesion and palatal myoclonus. Palatal tremor, also known as palatal myoclonus, is a rare movement disorder that has intrigued investigators since the 19th century. Symptomatic palatal tremor is usually the result of a lesion in the triangle of Guillain and Mollaret and is associated with hypertrophic olivary degeneration (HOD) that can be seen on MR images as enlargement of the inferior olivary nucleus (ION), with increased signal on T2- and proton density–weighted images. The triangle of Guillain and Mollaret is defined by three anatomic structures: the dentate nucleus, the red nucleus (although not functionally part of the circuit), and the ION. Fiber tractography showed decreased volume of the right central tegmental tract, supporting a diagnosis of HOD.
WINKING FROG SIGN: Look at the antero lateral medulla showing reduced CST color code and anisotropy. Seen in HOD and other CST degenerations (Both primary and secondary).Described first by Prof Sunaret et al in 2005.

Case submitted by Dr Rammohan Vadapalli, Senior Consultant Radiologist from Hyderabad.