Hyperreflexia

Hyperreflexia is an exaggerated deep tendon reflex response, exceeding normal briskness on examination. It is a sign of upper motor neuron involvement rather than a disease itself. Reflexes are typically graded 0–4+, and hyperreflexia is usually 3+ or 4+, often with clonus and a positive Babinski sign.

It results from loss of inhibitory control over spinal reflex circuits by descending corticospinal and brainstem pathways. This disinhibition is characteristic of upper motor neuron syndrome. In acute spinal cord injury, reflexes may be initially diminished (spinal shock) and later become hyperactive as recovery proceeds.

Causes include cerebrovascular accidents (stroke), traumatic brain or spinal cord injury, multiple sclerosis, and other disorders of the corticospinal tract. Less commonly, thyroid excess (hyperthyroidism) and certain medications can produce brisk reflexes.

Diagnosis relies on neurologic examination and imaging (often MRI) to identify structural lesions. Electrophysiologic studies and laboratory tests may help differentiate upper motor neuron from lower motor neuron disease and identify reversible contributors.

Treatment targets the underlying condition and management of spasticity: physical therapy, stretching, and pharmacologic agents such as baclofen, tizanidine, or dantrolene. Focal hyperreflexia may be treated with botulinum toxin; severe cases may require intrathecal baclofen. Prognosis depends on etiology and injury extent; hyperreflexia itself reflects central nervous system involvement and may improve with treatment of the primary disorder.