A 45-year-old man comes to the office for the evaluation of excessive wasting of his extremity muscles, which is more apparent on the extensor side. The weakness began distally and asymmetrically. He recently started to have difficulties with swallowing, chewing, and speaking. He feels some movements in his face and tongue. He also has muscle stiffness. His bowel, bladder, cognitive, and sensory functions are intact. The physical examination reveals excessive wasting of his muscles, which is more prominent in the lower extremities. Fasciculations and hyperreflexia are noted. His bulbar reflexes are decreased. What neural pathway is most likely damaged?

Question

A 45-year-old man comes to the office for the evaluation of excessive wasting of his extremity muscles, which is more apparent on the extensor side.  The weakness began distally and asymmetrically.  He recently started to have difficulties with swallowing, chewing, and speaking.  He feels some movements in his face and tongue.  He also has muscle stiffness.  His bowel, bladder, cognitive, and sensory functions are intact.  The physical examination reveals excessive wasting of his muscles, which is more prominent in the lower extremities.  Fasciculations and hyperreflexia are noted.  His bulbar reflexes are decreased.  What neural pathway is most likely damaged?

Quizplus · Accepted Answer

Explanation: This patient has amyotrophic lateral sclerosis (ALS), a devastating, progressive neurodegenerative disorder. It is characterized by the presence of both upper motor neuron (UMN) and lower motor neuron (LMN) lesions. Spasticity and exaggerated deep tendon reflexes are signs of UMN damage due to degeneration of frontal motor neurons and their axons. Corticobulbar tract damage due to UMN symptoms, sometimes described as pseudobulbar palsy, can cause dysarthria, dysphagia, and pseudobulbar affect (inappropriate laughing, crying). Fasciculations (sometimes manifesting as movements in the face and tongue), weakness, and atrophy indicate LMN damage in the brainstem and spinal cord. Dysarthria and dysphagia can also be due to LMN injury (ie, bulbar palsy) resulting in weakness of the tongue and other muscles. The soft palate reflex may be weak, particularly in bulbar-onset ALS. Asymmetric limb weakness is the most common presentation of ALS; bulbar symptoms (eg, dysarthria, dysphagia) are the second most common. However, the disease may manifest in any body segment (bulbar, cervical, thoracic, lumbosacral). (Choices A and E) Cerebral cortex and pyramidal tract (ie, corticobulbar and corticospinal tract) lesions would not explain the combination of UMN and LMN damage seen in this patient. Educational objective: Amyotrophic lateral sclerosis (ALS) is characterized by the presence of both upper (eg, spasticity, hyperreflexia) and lower (eg, fasciculations, atrophy) motor neuron lesions.

A 45-Year-Old Man Comes to the Office for the Evaluation