What does non dermatomal mean?

Answer 1

To understand non-dermatomal, you must first understand what a dermatome is.  

A dermatome is the region of skin that is perceived by a particular nerve root level.  Nerve roots come off of the entire length of the spinal cord.  These nerve roots are named by their region and their number from the top of the region.  The regions from top to bottom are called: cervical, thoracic, lumbar, sacral, and coccygeal.  Each region has its own individual nerve roots on each side: cervical has 8, thoracic has 12, lumbar has 5, sacral has 5, & coccygeal usually has 1.  

If a nerve is injured at the root a physician or chiropractor may note "dermatomal pattern pain" or "dermatomal pattern of sensory loss,"  implying that there has been a disturbance in normal sensation along that area of skin that is perceived by and carried within that nerve root.  For example a C7 dermatomal loss would include the middle finger, the back of the forearm, the back of the upper arm, and into the lower neck.  An L5 dermatomal loss might include the back or side of the thigh, the side of the calf, and the top of the foot.

Non-dermatomal refers to damage to a nerve in the periphery, distant to the root.  A nerve that is damaged in the arm or leg would cause a non-dermatomal sensory disturbance.  An example is the thumb along with middle and index fingers being affected with a median nerve injury in carpal tunnel syndrome, a little finger and part of the right finger being affected in an ulnar neuroapthy, or the side of the leg and the top of the foot being affected  in a peroneal neuropathy.  Each of those three examples refers to a peripheral  nerve being affected at a point distant to the nerve root.

Answer 2

A symptom is non-dermatomal when it does not follow the expected cutaneous distribution pattern associated with an injured spinal nerve root.