Arreflexia

Areflexia, sometimes spelled arreflexia, is the absence of reflex responses to a tendon tap or other reflex-eliciting stimulus. In clinical neurology, reflexes are scored on a scale from 0 to 4, where 0 denotes no reflex and 4 indicates a hyperactive reflex. Areflexia refers to a marked reduction or complete loss of the reflex response in the tested muscle group. It can be localized to a single reflex or generalized to multiple reflexes.

The presence or absence of reflexes helps distinguish types of nervous system pathology. Areflexia may result from disruption of any part of the reflex arc, including sensory afferents, the spinal cord or nerve roots, the motor neurons, or the muscles themselves. It can be transient, as in spinal shock after acute spinal cord injury, where reflexes are absent early but may later become hyperactive. Areflexia can also occur in peripheral nerve disorders, radiculopathies, motor neuron disease, or certain neuromuscular junction or toxin-related conditions. In some disorders, areflexia is a hallmark finding (for example, Guillain-Barré syndrome), while in others it may be present only in the affected region or be less pronounced.

Common etiologies include acute spinal cord injury with spinal shock, Guillain-Barré syndrome and other inflammatory neuropathies, radiculopathies and peripheral neuropathies, certain toxin exposures (such as botulism), and less commonly central or neuromuscular junction disorders. Evaluation typically involves a thorough neurological exam, neurophysiological testing (nerve conduction studies and EMG), imaging as indicated, and laboratory studies to identify the underlying cause. Prognosis depends on the etiology and the extent of neural injury.