neurologic disorders
How to Assess Reflexes
Other reflexes
Testing forclonus(rhythmic, rapid alternation of muscle contraction and relaxation caused by sudden, passive tendon stretching) is done by rapid dorsiflexion of the foot at the ankle. Sustained clonus indicates an upper motor neuron disorder. Thesuperficial abdominal reflexis elicited by lightly stroking the 4 quadrants of the abdomen near the umbilicus with a wooden cotton applicator stick or similar tool. The normal response is contraction of the abdominal muscles causing the umbilicus to move toward the area being stroked. Stroking the skin toward the umbilicus is recommended to rule out the possibility that movement was caused by the skin being dragged by the stroking. Depression of this reflex may be due to a central lesion, obesity, or lax skeletal muscles (eg, after pregnancy); its absence may indicate spinal cord injury. Sphincteric reflexesmay be tested during the rectal examination. To test sphincteric tone (S2 to S4 nerve root levels), the examiner inserts a gloved finger into the rectum and asks the patient to squeeze it. Alternatively, the perianal region is touched lightly with a cotton wisp; the normal response is contraction of the external anal sphincter (anal wink reflex). Rectal tone typically becomes lax in patients with acute spinal cord injury or cauda equine syndrome. For thebulbospongiosus reflex, which tests S2 to S4 levels, the dorsum of the penis is tapped; normal response is contraction of the bulbospongiosus muscle. For thecremasteric reflex, which tests the L2 level, the medial thigh 7.6 cm (3 in) below the inguinal crease is stroked upward; normal response is elevation of the ipsilateral testis. 