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 (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 (clinically known as the umbilicus; : umbilici or umbilicuses; also known as the belly button or tummy button) is a protruding, flat, or hollowed area on the abdomen at the attachment site of the umbilical cord. Structure The u ...

. 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 of intermediate size between the cervical and lumbar ve ...

. Pathological absence can be due to: *

Multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

Motor neuron disease Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or—in the United States—Lou Gehrig's disease (LGD), is a rare, terminal neurodegenerative disorder that results in the progressive loss of both upper and low ...

(late) * Neurogenic bladder *

Brown-Séquard syndrome Brown-Séquard syndrome (also known as Brown-Séquard's hemiplegia, Brown-Séquard's paralysis, hemiparaplegic syndrome, hemiplegia et hemiparaplegia spinalis, or spinal hemiparaplegia) is caused by damage to one half of the spinal cord, i.e. hem ...

* 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 Medical signs