A 65-year-old man is evaluated for a 6-month history of unsteady gait. His balance has become so poor that he requires the use of a cane. The patient also has paresthesias in his hands and feet, which started a year ago. He has a medical history of lumbar spinal stenosis, hypertension, and hyperlipidemia. The patient has a 30-pack-year smoking history and does not use alcohol or illicit drugs.
Blood pressure is 143/90 mm Hg and heart rate is 82/min. Neurologic examination reveals a distal greater than proximal reduction in pain and temperature sensation, vibration, and proprioception in the lower and upper extremities. Muscle bulk, tone, and strength are normal. Ankle reflexes are absent with downgoing plantar responses. His gait is high-stepping, and Romberg sign is positive. Laboratory results are as follows:
Which of the following tests is most likely to establish the diagnosis in this patient?

Question

A 65-year-old man is evaluated for a 6-month history of unsteady gait.  His balance has become so poor that he requires the use of a cane.  The patient also has paresthesias in his hands and feet, which started a year ago.  He has a medical history of lumbar spinal stenosis, hypertension, and hyperlipidemia.  The patient has a 30-pack-year smoking history and does not use alcohol or illicit drugs.
Blood pressure is 143/90 mm Hg and heart rate is 82/min.  Neurologic examination reveals a distal greater than proximal reduction in pain and temperature sensation, vibration, and proprioception in the lower and upper extremities.  Muscle bulk, tone, and strength are normal.  Ankle reflexes are absent with downgoing plantar responses.  His gait is high-stepping, and Romberg sign is positive.  Laboratory results are as follows:
 Which of the following tests is most likely to establish the diagnosis in this patient?

Quizplus · Accepted Answer

This patient's clinical features of bilaterally progressive distal sensory loss, ankle areflexia, and high-stepping ataxic gait with positive Romberg sign (reflecting loss of proprioceptive function) are consistent with peripheral neuropathy. Peripheral neuropathy can be caused by a variety of conditions, with diabetes mellitus and alcohol abuse being among the most common. Up to one-third of cases are idiopathic. conditions Diagnostic evaluation should be considered in patients when the etiology of neuropathy is unclear or in the setting of severe or rapidly developing symptoms. The initial workup may include laboratory studies such as blood glucose, vitamin B₁₂, TSH, antinuclear antibody, rapid plasma reagin, hemoglobin A1c, erythrocyte sedimentation rate, complete blood count, and serum protein electrophoresis. ₁₂ This patient's normocytic anemia and hypercalcemia raise suspicion for paraproteinemic neuropathy due to a plasma cell dyscrasia (eg, multiple myeloma). (Choice A) Lumbar puncture may be used to diagnose tabes dorsalis, a form of neurosyphilis that primarily affects the posterior columns and causes sensory ataxia and a positive Romberg sign. However, tabes dorsalis typically presents with lancinating pains and Argyll-Robertson pupil; anemia and hypercalcemia are not associated with this disease. (Choice B) Patients with disseminated Lyme disease may develop neurologic manifestations such as peripheral neuropathy; however, other characteristic features such as erythema migrans, arthritis, and carditis are not evident in this patient. (Choice C) MRI of the brain and spine is unlikely to be diagnostically useful given this patient's bilaterally symmetric sensory deficits and absence of upper motor neuron signs (eg, hyperreflexia, spasticity) or cerebellar dysfunction. The Romberg test (noting whether patients can maintain their balance with both feet together after closing their eyes) assesses proprioceptive ability, not cerebellar function (which is sometimes evaluated by pronator drift); a high-stepping gait and positive Romberg sign indicate likely neuropathic disease. Patients with cerebellar ataxia often cannot maintain balance regardless of visual cues. Romberg test pronator drift (Choice E) Porphyrias may cause a neuropathy but usually present with acute neurovisceral symptoms (eg, abdominal pain, psychiatric symptoms, autonomic dysfunction) and/or a chronic photosensitive rash. This patient's absence of other neurovisceral symptoms or rash makes the diagnosis unlikely. Educational objective: Diagnostic evaluation of peripheral neuropathy should be considered in patients when the etiology of neuropathy is unclear or in the setting of severe or rapidly developing symptoms. The initial workup may include laboratory studies such as blood glucose, vitamin B₁₂, TSH, antinuclear antibody, rapid plasma reagin, hemoglobin A1c, erythrocyte sedimentation rate, complete blood count, and serum protein electrophoresis. ₁₂ __________ References: Polyneuropathy associated with IgM vs IgG monoclonal gammopathy: comparison between clinical and electrophysiological findings. (http://www.ncbi.nlm.nih.gov/pubmed/20003083) Neuropathy and paraproteins: review of a complex association. (http://www.ncbi.nlm.nih.gov/pubmed/21418441) Paraproteinemic neuropathy. (http://www.ncbi.nlm.nih.gov/pubmed/19637090)

A 65-Year-Old Man Is Evaluated for a 6-Month History of Unsteady