DR.MOHAMMED IRFAN SHEIKH11 months ago

Hung-up Knee Jerk in Huntington’s Disease

A 54-year-old woman presented to the neurology clinic with progressively worsening gait disturbance over the course of 2 years. She had a history of hypothyroidism after a thyroidectomy for papillary thyroid cancer; she was currently euthyroid while receiving levothyroxine therapy. Physical examination revealed generalized chorea, motor impersistence of tongue protrusion, mild dementia, disinhibition, irritability, and deep-tendon hyperreflexia. Notably, her legs remained extended for several seconds after stimulation of the patellar tendon, a finding referred to as the hung-up knee jerk (see video). A magnetic resonance image of the head showed slight atrophy of the caudate nuclei, and genetic testing revealed expanded CAG repeats in HTT, a finding consistent with the diagnosis of Huntington’s disease. In addition to occurring in some patients with Huntington’s disease, the hung-up knee jerk can also be observed in patients with Sydenham’s chorea or benign hereditary chorea and must be distinguished from the delayed relaxation of deep-tendon reflexes that can be seen in patients with hypothyroidism. The patient was treated with haloperidol, and the hung-up knee jerk resolved.