CASE 52

By: Dr. Subramaniyan Ramanathan MD and Dr. Mahmoud Alheidous. 

HISTORY: 55-year-old female with paresthesia in the hand with some subjective weakness.

What are your findings?

What is the differential diagnosis?

What are the causes?

FINDINGS:

Serial axial T2W MRI of carpal tunnel shows flattening of the median nerve distally. Palmar bowing of flexor retinaculum is well seen at the level of hook of hamate. Proximally there is enlargement and edema of the median nerve.

DIAGNOSIS:

Carpal tunnel syndrome.

PEARLS AND DISCUSSION:

Carpal tunnel syndrome (CTS), compression of the median nerve as it courses through the carpal tunnel, is the most common entrapment neuropathy in the body. It is more common in females with female to male ratio of 3-5:1. CTS typically occur between the ages of 30 and 60 years and can be bilateral in up to 50% of patients. It can either result from an abnormality that decreases the size of the tunnel or that enlarges the contents of the tunnel. Osteoarthritis, trauma, acromegaly, and mechanical overuse can reduce the capacity of carpal tunnel, whereas ganglion cysts, nerve sheath tumours, amyloidosis or synovial hypertrophy in rheumatoid arthritis can lead to increase in the size of the contents.

Clinically, patients complain of nocturnal pain, hand clumsiness, tingling, and numbness in the median nerve distribution. Imaging is used when the syndrome is suspected in the face of a negative nerve conduction test or when history and physical examination suggest a space-occupying lesion within the carpal tunnel.

Both ultrasonography and MRI are helpful in the diagnosis. Imaging triad includes:

• Palmar bowing of the flexor retinaculum (>2 mm beyond a line connecting the pisiform and the scaphoid).

• Distal flattening of the nerve.

• Enlargement of the nerve proximal to the flexor retinaculum.

Other signs are loss of fat within the carpal tunnel, increased size/oedema of the nerve on water-sensitive sequences (called as Pseudo neuroma appearance), and, in some cases, contrast enhancement of the nerve.

FURTHER READING:

1. Miller TT, Reinus WR. Nerve entrapment syndromes of the elbow, forearm, and wrist. AJR Am J Roentgenol. 2010;195 (3): 585-94

2. Tsujii M, Hirata H, Morita A et-al. Palmar bowing of the flexor retinaculum on wrist MRI correlates with subjective reports of pain in carpal tunnel syndrome. J Magn Reson Imaging. 2009;29 (5): 1102-5

3. Mesgarzadeh M, Triolo J, Schneck CD. Carpal tunnel syndrome. MR imaging diagnosis. Magn Reson Imaging Clin N Am. 1995;3 (2): 249-64