Okay, let's tackle this question. The patient is a 57-year-old woman with symptoms of numbness and tingling in her right thumb, index, and middle finger. She wakes up at night with these symptoms and needs to shake her hand to relieve them. Physical exam shows decreased sensation in those areas, and symptoms are reproduced with Tinel's test and exacerbated by wrist hyperflexion. No motor weakness.

First, I need to recall the common causes of these symptoms. The distribution of numbness in the thumb, index, and middle fingers points to the median nerve. The median nerve innervates these areas, so issues like carpal tunnel syndrome (CTS) come to mind. CTS is the most common entrapment neuropathy, caused by compression of the median nerve at the wrist. The classic symptoms are numbness in the distribution of the median nerve, which matches the patient's complaints. Tinel's sign, which is a tingling sensation when tapping over the nerve, is positive here, and Phalen's maneuver (which involves wrist flexion) exacerbates symptoms, both of which are diagnostic for CTS.

Other options might include cervical radiculopathy, but the patient denies neck or arm pain, and symptoms are only in one hand without leg involvement. Ulnar nerve entrapment would affect the little and ring fingers, not the thumb, index, and middle. Radial nerve issues usually cause sensory loss over the back of the hand and involve motor deficits, which aren't present here. Thoracic outlet syndrome could cause similar symptoms but typically affects both upper extremities and may have other systemic symptoms.

The key here is the specific nerve distribution and the positive Tinel's and Phalen's signs. The clinical pearl is that CTS is often associated with nighttime symptoms and specific physical exam findings. The correct answer is carpal tunnel syndrome.

**Core Concept**
This question tests recognition of **carpal tunnel syndrome (CTS)**, a median nerve entrapment neuropathy. The median nerve supplies sensory innervation to the palmar aspect of the thumb, index, and middle fingers (excluding the distal pulp), and motor function to the thenar muscles. Compression occurs at the carpal tunnel, a narrow anatomical space in the wrist.

**Why the Correct Answer is Right**
The patient’s symptoms—nocturnal numbness/tingling in the median nerve distribution, relief by shaking the hand, and exacerbation with wrist flexion—are classic for **carpal tunnel syndrome**. **Tinel’s sign** (tingling from tapping over the median nerve) and **Phalen’s maneuver** (pain/numbness with wrist flexion) are diagnostic clues. The absence of motor weakness and leg involvement further supports a focal entrapment rather than a radiculopathy or systemic neuropathy.

**Why Each Wrong Option is Incorrect**
**Option A:** *Cervical radiculopathy* would cause neck/shoulder pain and sensory/motor deficits in a dermatomal pattern across both limbs. The patient has no neck pain or bilateral symptoms.
**Option B:** *Ulnar nerve entrapment* affects the medial forearm, little finger, and ulnar half of the ring finger. The patient’s symptoms are in the thumb/index/middle fingers.
**Option C:** *Radial nerve injury* typically causes sensory loss over the dorsum of the

✓ Correct Answer: B. Carpal tunnel syndrome