CASE 150
By: Dr. Nizar Al-Nakshabandi MD, FRCPC
HISTORY: 47-year-old female with hand pain.
What are your findings?
What is the differential diagnosis?
What are the causes?
FINDINGS:
Median nerve at the carpal tunnel measures 14 mm², and proximally at the level of the pronator quadratus measures 10 mm2, a difference of 4 mm². Carpal tunnel contents are normal. Flexor and extensor tendons are unremarkable.
DIFFERENTIAL DIAGNOSIS:
· Carpal tunnel syndrome.
· Pronator teres syndrome.
· Anterior interosseous nerve syndrome.
DIAGNOSIS:
Carpal tunnel syndrome.
PEARLS AND DISCUSSION:
Carpal tunnel syndrome is from compression of the median nerve within the carpal tunnel.
It affects approximately 4% of the adult population.
Usually affects women 5 times more than men and spans in age from this third decade to the sixth decade.
It can be bilateral in approximately 30-50% of cases.
It can be mixed up with pronator teres syndrome. Causes usually are osteoarthritis, trauma, overuse and acromegaly, and sometimes ganglions in the carpal tunnel can compress on the median nerve and cause it. Synovial hypertrophy in rheumatoid arthritis has been implicated.
On ultrasound, palmar bowing of the flexor retinaculum can be seen. Distal flattening of the nerve. Enlargement of the nerve proximal to the flexor retinaculum.
Enlargement of the nerve seems to be the most sensitive and specific criterion. The normal cross-sectional area of the median nerve is between 9 and 11 mm².
A study calculated a 2 mm2 difference in nerve cross-section between the level of the pronator quadratus and carpal tunnel having a 99% sensitivity and 100% specificity for carpal tunnel syndrome.
MRI can show the bowing out of the flexor retinaculum and enlargement of the median nerve at the level of the pisiform as well as flattening of the median nerve at the level of hamate. MRI is superior to detect masses and arthritis.
Treatment is by splinting and nonsteroidal anti-inflammatory drugs. Corticosteroid injection into the carpal tunnel can alleviate the symptoms temporarily for up to 3 months. Surgical release of the flexor retinaculum has been done.
FURTHER READING:
1. Mesgarzadeh M, Schneck CD, Bonakdarpour A et-al. Carpal tunnel: MR imaging. Part II. Carpal tunnel syndrome. Radiology. 1989;171 (3): 749-54. Radiology (abstract) - Pubmed citation
2. Campagna R, Pessis E, Feydy A et-al. MRI assessment of recurrent carpal tunnel syndrome after open surgical release of the median nerve. AJR Am J Roentgenol. 2009;193 (3): 644-50. AJR Am J Roentgenol (full text) - doi:10.2214/AJR.08.1433 - Pubmed citation
3. Wong SM, Griffith JF, Hui AC et-al. Carpal tunnel syndrome: diagnostic usefulness of sonography. Radiology. 2004;232 (1): 93-9. Radiology (full text) - doi:10.1148/radiol.2321030071
