An abdominal reflex is a superficial neurological
reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
stimulated by stroking of the abdomen around the
umbilicus. It can be helpful in determining the level of a
central nervous system (CNS) lesion. Being a superficial reflex, it is
polysynaptic
A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neuron ...
(involving multiple connections between nerves).
Test
The abdomen is mentally divided into four quadrants, and the skin in each quadrant is gently stroked, on the diagonal, towards the
navel.
The navel should twitch towards the stimulus.
Roots involved
Thoracic 8th – 12th segments are involved.
Absent abdominal reflex
Abdominal reflex is noted as either present or absent. An absent response can be physiological. Physiological absent response can be due to obesity,
frailty, or muscle laxity after
multiple pregnancies or abdominal surgery.
It is not unusual for this reflex to be absent in children.
If the reflex is absent, or especially if it is asymmetric, it can indicate a neurological problem somewhere above the lower
thoracic spine
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
.
Pathological absence can be due to:
*
Multiple sclerosis
Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This d ...
*
Motor neuron disease (late)
*
Neurogenic bladder
*
Brown-Séquard syndrome
*
Chiari malformations
Evolutionary significance
The local contraction of the abdominal muscles to an abdominal sensory stimulus was to protect the internal viscera from damage.
References
{{Reflex
Reflexes