Both superficial and deep abdominal reflexes are described, of which the superficial (cutaneous) reflexes are the more commonly tested in clinical practice. A wooden stick or pin is used to scratch the abdominal wall, from the flank to the midline, parallel to the line of the dermatomal strips, in upper (supraumbilical), middle (umbilical), and lower (infraumbilical) areas. The maneuver is best performed at the end of expiration when the abdominal muscles are relaxed, since the reflexes may be lost with muscle tensing; to avoid this, patients should lie supine with their arms by their sides.
Superficial abdominal reflexes are lost in a number of circumstances:
- normal old age
- after abdominal surgery
- after multiple pregnancies
- in acute abdominal disorders ( Rosenbach’s sign ).
However, absence of all superficial abdominal reflexes may be of localizing value for corticospinal pathway damage (upper motor neurone lesions) above T6. Lesions at or below T10 lead to selective loss of the lower reflexes with the upper and middle reflexes intact, in which case Beevor’s sign may also be present. All abdominal reflexes are preserved with lesions below T12.
Abdominal reflexes are said to be lost early in multiple sclerosis, but late in motor neurone disease, an observation of possible clinical use, particularly when differentiating the primary lateral sclerosis variant of motor neurone disease from multiple sclerosis. However, no prospective study of abdominal reflexes in multiple sclerosis has been reported.
- Dick JP. The deep tendon and the abdominal reflexes. J Neurol Neurosurg Psychiatry 2003 Feb; 74(2) 150-3. pmid:12531937.