Dermatomes and Myotomes

A 52-year-old woman with diabetes presents with progressive weakness of the right lower limb over 3 weeks. On examination, she has weakness of hip flexion (iliopsoas, L1–L2), knee extension (quadriceps, L3–L4), and ankle dorsiflexion (tibialis anterior, L4–L5). Sensory loss is noted over the right anterior thigh and medial leg (L3–L4 dermatomes). She denies bowel or bladder symptoms. MRI lumbar spine shows a large disc herniation at L4–L5 with nerve root compression. What is the most appropriate next step in management?

A 52-year-old man from Delhi presents to the emergency department with acute onset severe pain in the right shoulder and upper arm, radiating down the lateral aspect of the arm to the thumb and index finger. On examination, he has weakness of shoulder abduction and external rotation. Sensory testing reveals diminished sensation over the lateral shoulder and dorsal aspect of the first web space. His reflexes are intact. What is the most likely nerve root involved?

A 68-year-old woman from Mumbai presents with progressive weakness and atrophy of the intrinsic muscles of her right hand over the past 3 months. She reports numbness and tingling in the medial 1.5 fingers (ring and little fingers) and the medial aspect of the palm. On examination, there is marked wasting of the hypothenar eminence and interossei. Grip strength is severely reduced. What is the most likely nerve root and dermatome involved?

A 38-year-old man presents with sudden-onset severe pain radiating from the lower back to the lateral aspect of the right leg and foot. On examination, there is weakness of ankle dorsiflexion and sensory loss over the dorsum of the foot and lateral leg. Which is the most common site of nerve root compression causing this clinical presentation?

During a clinical examination of dermatomes, a medical student is asked to identify the most common dermatome affected in a patient with herpes zoster (shingles) in the thoracic region. Which of the following is the most frequent site of thoracic herpes zoster?