Dissociation of the abdominal reflexes
There are two types of abdominal reflexes, superficial and deep. The superficial abdominal reflexes consist of contraction of the abdominal muscles elicited by a light stroke or scratch of the anterior abdominal wall that pulls the umbilicus in the direction of the stimulus.(1-3) The deep abdominal muscle stretch reflexes are elicited by pressing down slightly on the anterior abdominal wall with the fingers, then tapping with a reflex hammer, which causes reflex muscle contraction. The abdominal muscle stretch reflexes are only minimally present in normal individuals.
Dissociation of reflexes is a difference in the activity level of the DTRs and the superficial reflexes. Brisk deep abdominal reflexes with absent superficial abdominal reflexes, termed dissociation of the abdominal reflexes, suggests a corticospinal tract lesion.(4) See Video A.1 from reference 2 for a demonstration. Dissociated abdominal reflexes can provide crude localization in disorders of the thoracic spinal cord, but are less reliable than a sensory level to pin prick.(3)
The video shows dissociation of the abdominal reflexes in a patient with a mild paraparesis following an episode of transverse myelitis involving the thoracic cord.
1. Campbell WW. DeJong's the neurologic examination, 7th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2013.
2. Campbell WW. Clinical signs in neurology: a compendium. Philadelphia: Wolters Kluwer Health, 2016.
3. Dick JP. The deep tendon and the abdominal reflexes. J Neurol Neurosurg Psychiatry 2003;74:150–153.
4. Lehoczky T, Fodors T. Clinical significance of the dissociation of abdominal reflexes. Neurology 1953;3:453.