A 45-year-old man comes to the clinic due to a 2-month history of progressive left arm clumsiness and weakness. The patient initially attributed his symptoms to a left rotator cuff injury he sustained several years ago; however, he has recently developed problems with his gait. The patient's symptoms have interfered with daily activities such as bathing and dressing. He has had no recent injury, headaches, or bowel/bladder symptoms. On physical examination, there is reduced muscle strength in the left upper extremity. Further evaluation with brain MRI reveals a lesion involving the corticospinal tract. Which of the following additional signs is most likely to been seen in this patient?

Question

A 45-year-old man comes to the clinic due to a 2-month history of progressive left arm clumsiness and weakness.  The patient initially attributed his symptoms to a left rotator cuff injury he sustained several years ago; however, he has recently developed problems with his gait.  The patient's symptoms have interfered with daily activities such as bathing and dressing.  He has had no recent injury, headaches, or bowel/bladder symptoms.  On physical examination, there is reduced muscle strength in the left upper extremity.  Further evaluation with brain MRI reveals a lesion involving the corticospinal tract.  Which of the following additional signs is most likely to been seen in this patient?

Quizplus · Accepted Answer

11ec160b_39a9_e759_9249_471432fd8c40_MD0001_00 Voluntary muscle activity is mediated by the corticospinal (pyramidal) tracts. First-order neurons of these tracts are located in the premotor and motor cortex of the frontal lobe (Brodmann areas 6 and 4, respectively). Their efferent fibers descend through the internal capsule, midbrain, and pons, and continue to form the pyramids on the anterior aspect of the medulla. In the medulla, 90% of the fibers decussate (cross) to form the lateral corticospinal tract. Fibers that do not decussate descend as the anterior corticospinal tract. The axons of both tracts synapse on the motor neurons of the anterior horn (second-order neurons). Damage to the corticospinal tract is divided into upper and lower motor neuron lesions: Combined UMN and LMN lesions are characteristic of amyotrophic lateral sclerosis (Lou Gehrig disease). (Choice E) Resting tremor is characteristic of Parkinson disease, which occurs due to loss of dopaminergic neurons in the substantia nigra. (Choice F) Sensory information is transmitted by the spinothalamic tract (pain and temperature) and dorsal column pathway (vibration and proprioception). Lesions to the corticospinal tract do not cause sensory deficits. Educational objective: Upper motor neuron damage leads to spastic paralysis, hyperreflexia, and an upgoing plantar reflex (Babinski sign) due to loss of descending inhibition over lower motor neurons in the anterior horn. Conversely, lower motor neuron lesions cause flaccid paralysis, hypotonia, hyporeflexia, muscle atrophy, and fasciculations. __________ References: Spastic hypertonia and movement disorders: pathophysiology, clinical presentation, and quantification. (http://www.ncbi.nlm.nih.gov/pubmed/19769916) The pathophysiology of spasticity. (http://www.ncbi.nlm.nih.gov/pubmed/11918643)

A 45-Year-Old Man Comes to the Clinic Due to a 2-Month