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Friday, February 23, 2007

Lower back pain| sensory | lower limb

When your lower back hurts and you feel tingling, numbness or abnormal sensations in the lower limb limb including the foot and toes, there may be irritation of the sensory portion of the lower back nerve roots and/or the peripheral nerves supplying those regions.

However, pain in an area is often related to tightness and spasm of the underlying muscles due to motor nerve root irritation that may not correspond to the dermatome in that area from sensory nerve root irritation.

The sensory distribution (dermatomes) of the lower limb are carried through by the peripheral nerves of the lumbosacral plexus. At a later date, we will talk about the lumbosacral plexus (a network of interlacing nerves going to the lower limb from the lower back).

Dermatomes:

Front and outer aspect of the thigh: L2 (via the lateral femoral cutaneous nerve of the thigh)

Inner aspect of the thigh and front of the knee: L3 (via the obturator nerve)

Inner aspect of the leg: L4 (via the saphenous nerve)

Outer aspect of the leg and top of the foot and first three toes: L5 (via the peroneal nerve)

Middle area of lower half of the back of the leg, heel and last two toes: S1 (via the sural nerve)

Back of the thigh to the middle of the upper half of the calf: S2 (via the posterior femoral cutaneous nerve of the thigh)

Front and outer aspect of the thigh is L2 dermatome; inner aspect of the thigh and front of the knee is L3 dermatome (below)

L2, L3 dermatomes

Back of the thigh to the middle of the upper half of the calf is S2 dermatome (below)

back of thigh showing S2 and L3 dermatomes

Inner aspect of the leg is L4 dermatome; outer aspect of the leg and top of the foot and first three toes is L5 dermatome; middle area of lower half of the back of the leg, heel and last two toes is S1 dermatome (below)

L4, L5 and S1 dermatomes