L5 pinprick loss finding
This patient has pinprick sensory loss over the lateral shin and big toe in the L5 dermatome.
[Doctor] Sharp or dull?
[Patient] Sharp.
[Doctor] Sharp or dull?
[Patient] Sharp.
[Doctor] Sharp or dull?
[Patient] Dull.
[Doctor] Sharp or dull?
[Patient] Dull.
[Doctor] Sharp or dull?
[Patient] Sharp.
[Doctor] Thank you.”
About L5 pinprick loss
Patients may also have loss of sensation in a focal area of skin within a limb or over the trunk corresponding to a dermatome. This pattern of sensory loss is most easily detected using pinprick stimulation. Knowledge of the distribution of the dermatomes aids in the performance and interpretation of the sensory exam. The big toe and lateral shin lie within the L5, or fifth lumbar, dermatome.
Localization
A dermatome is a segment of skin supplied by a single nerve root. L5 dermatomal pinprick loss is due to dysfunction of the fifth lumbar nerve root, also known as an L5 radiculopathy. Nerve root compression by a herniated disc or osteophyte is the most common cause of radiculopathy.