A 70-year-old man comes to the office due to weakness and clumsiness of his left leg. The patient's family noticed him dragging the left foot over the past several days, and he fell when his toes caught on a step. He has had no fever, headache, numbness, or visual disturbances. The patient has a history of lacunar infarction causing left-sided hemiparesis several years ago, which improved with physical therapy. His other medical problems include hypertension, type 2 diabetes mellitus, osteoarthritis, and chronic back pain attributed to osteoarthritis. The patient has lived alone since the death of his wife 4 years ago.
Temperature is 36.7 C (98.1 F), blood pressure is 136/88 mm Hg, pulse is 80/min, and respirations are 16/min. Examination shows moist mucous membranes, normal jugular venous pressure, clear lung fields, and normal heart sounds. The abdomen is soft and nontender. Cranial nerve examination is normal. Motor power is 5/5 in both upper and right lower extremities. There is reduced strength of left leg abduction, left foot inversion and eversion, and toe extension. Bilateral upper and lower extremity deep tendon reflexes are normal. While walking, the patient flexes his left thigh higher and his left foot slaps the floor.
Which of the following is most appropriate next step in evaluation of this patient's current symptoms?

Question

A 70-year-old man comes to the office due to weakness and clumsiness of his left leg.  The patient's family noticed him dragging the left foot over the past several days, and he fell when his toes caught on a step.  He has had no fever, headache, numbness, or visual disturbances.  The patient has a history of lacunar infarction causing left-sided hemiparesis several years ago, which improved with physical therapy.  His other medical problems include hypertension, type 2 diabetes mellitus, osteoarthritis, and chronic back pain attributed to osteoarthritis.  The patient has lived alone since the death of his wife 4 years ago.
Temperature is 36.7 C (98.1 F), blood pressure is 136/88 mm Hg, pulse is 80/min, and respirations are 16/min.  Examination shows moist mucous membranes, normal jugular venous pressure, clear lung fields, and normal heart sounds.  The abdomen is soft and nontender.  Cranial nerve examination is normal.  Motor power is 5/5 in both upper and right lower extremities.  There is reduced strength of left leg abduction, left foot inversion and eversion, and toe extension.  Bilateral upper and lower extremity deep tendon reflexes are normal.  While walking, the patient flexes his left thigh higher and his left foot slaps the floor.
Which of the following is most appropriate next step in evaluation of this patient's current symptoms?

Quizplus · Accepted Answer

Foot drop is due to weakness of the anterior tibialis muscle. It is most often due to common peroneal nerve injury or L5 radiculopathy; these conditions share similar clinical features (the common peroneal nerve originates from L5-S1) but may be distinguished by the presence of back pain and extent of weakness: Common peroneal nerve compression: Weakness of foot dorsiflexion, eversion, and toe extension. Pain is uncommon.L5 radiculopathy: More extensive weakness involving foot dorsiflexion, eversion, and inversion; toe extension; and possible weakness of leg abduction. Back pain radiating down the leg is common. Common peroneal nerve compression: Weakness of foot dorsiflexion, eversion, and toe extension. Pain is uncommon. Common peroneal nerve compression: Weakness of foot dorsiflexion, eversion, and toe extension. Pain is uncommon. L5 radiculopathy: More extensive weakness involving foot dorsiflexion, eversion, and inversion; toe extension; and possible weakness of leg abduction. Back pain radiating down the leg is common. L5 radiculopathy: More extensive weakness involving foot dorsiflexion, eversion, and inversion; toe extension; and possible weakness of leg abduction. Back pain radiating down the leg is common. Sensation may be decreased along the lateral leg and dorsum of the foot in both disorders, and reflexes are typically normal. This patient with back pain (attributed to osteoarthritis) and extensive deficits likely has a lumbosacral (L5) radiculopathy. Younger patients with radiculopathy typically have acute, severe pain and weakness from a herniated disk, whereas elderly patients often have more gradual, progressive symptoms due to osteophyte formation, foraminal stenosis and degenerative changes of the intervertebral discs and facet joints. MRI of the lumbar spine can show compression of the nerve root. Although immediate imaging is not necessary for most patients with acute uncomplicated radiculopathy, it is appropriate for an elderly patient with significant neurologic deficits and a history of falls. foraminal stenosis (Choice A) Noncontrast CT scan of the brain is indicated to evaluate acute stroke. Although a stroke can cause leg weakness, patients usually have more widespread weakness (hemiparesis) and are often hyperreflexic. (Choice B) Diabetes can cause a Charcot joint, which can cause foot drop, but patients typically have erythema, swelling, and warmth over the affected foot. Weakness of leg abduction would be unexpected. (Choice D) Nerve conduction studies can confirm peroneal neuropathy as the cause of foot drop, but this patient's findings suggest radiculopathy, so an MRI should be done first. (Choice E) Vitamin B₁₂ deficiency can cause gait disturbances but typically causes a symmetric distal sensory neuropathy. Neuropsychiatric changes and glossitis may also be present, but unilateral radicular symptoms are unusual. ₁₂ Educational objective: Foot drop is usually due to common peroneal nerve injury or L5 lumbosacral radiculopathy. Common peroneal nerve compression causes painless weakness of foot dorsiflexion, eversion, and toe extension; L5 radiculopathy usually causes back pain with more extensive weakness involving foot dorsiflexion, eversion and inversion; toe extension; and leg abduction. MRI in lumbosacral radiculopathy can show nerve root compression. __________ References: Lumbosacral radiculopathy. (http://www.ncbi.nlm.nih.gov/pubmed/28613587)

A 70-Year-Old Man Comes to the Office Due to Weakness