11834
A 64-year-old man comes to the office due to progressive low back pain for the past several months that is beginning to interfere with his job. The patient describes pain in the lower back and buttocks, which worsens with prolonged standing or walking and improves with lying down. He also has occasional sharp, shooting pain that radiates down his right leg. The patient works as a greeter for a local supermarket and was recently given a written warning for taking too many breaks during his shift. He has a history of hypertension and osteoarthritis. Spine imaging reveals degenerative joint changes and a large osteophyte compressing the spinal nerve root exiting through the right neural foramen between the L5 and S1 vertebrae. Which of the following examination findings is most likely present in this patient due to the nerve lesion?
A.Decreased knee reflex
B.Decreased rectal tone
C.Sensory loss in inguinal region
D.Weakness of foot dorsiflexion
E. Weakness of hip flexion
THE CORRECT ANSWER IS : D.
Weakness of foot dorsiflexion
EXPLANATION
This patient has lumbosacral radiculopathy due to an osteophyte at the L5-S1 neural foramen resulting in compression of the L5 nerve root. Spinal nerves in the lumbosacral spine exit below their corresponding vertebral body level (eg, L5 nerve root exits between L5 and S1 vertebral bodies). However, because of the presence of multiple spinal nerve roots in the lumbosacral area (ie, cauda equina), nerve root compression can occur at different vertebral levels through 2 distinct mechanisms:
Spinal spondylosis: Degenerative changes and osteophyte formation can narrow the neural foramina. This leads to nerve root compression as it passes through the neural foramina (in this patient, an osteophyte is compressing the exiting L5 nerve root).
Vertebral disc herniation: A tear in the intervertebral disc annulus can lead to herniation of the nucleus pulposus. If this occurs laterally, it can compress the exiting nerve root as it passes through the neural foramina. However, if it occurs more centrally, it can protrude into the spinal canal and compress other nerves in the cauda equina that exit one or more levels below the area of herniation.
L5 radiculopathy causes sensory loss and back pain that radiates down the leg in an L5 dermatomal distribution (eg, buttocks, lateral thigh and calf, dorsal foot). Weakness occurs in muscles innervated by fibers from the L5 spinal root, which include the tibialis anterior (foot dorsiflexion and inversion), peroneus (foot eversion), and extensor hallucis longus (great toe extension).
Subject: anatomy
System: Nervous System
Topic: AR
