Swollen Nerve
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
- • Best to identify nerve at specific location, then follow it distally or proximally in transverse plane
- • When assessing nerve compression, important to measure cross-sectional area of nerve at specific locations
- • When assessing noncompressive nerve disorder, comparison with asymptomatic contralateral side is very helpful
- • Nerve measurements are ~ 20% smaller on US than MR
Helpful Clues for Common Diagnoses
- • Nerve Entrapment
- • Nerve Sheath Tumor
Tumor of peripheral nerve
Hypoechoic, fusiform-shaped tumor of nerve
Thickening of entering or exiting nerve
Anechoic areas
Posterior acoustic enhancement
Moderately hyperemic on Doppler
± hyperechoic areas
Malignant peripheral nerve sheath tumor is more likely if
FDG PET has quite high (~ 80-90%) sensitivity and specificity for diagnosing malignant peripheral nerve sheath tumor associated with neurofibromatosis
Helpful Clues for Less Common Diagnoses
- • Nerve I njury
- • Perineural Fibrosis
- • Immune-Mediated Peripheral Neuropathy
Chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal mononeuropathy (MMN) are acquired immune-mediated peripheral neuropathies
- – Aberrant immune response
- – CIDP affects sensory and motor function bilaterally and all 4 limbs
- – MMN is purely motor and usually affects only upper limbs
- – Neural enlargement seen on US, particularly proximally and in nonentrapment sites
- – Examination of vagus nerve in neck (> 2 mm²), median nerve in midupper arm (> 13.8 mm²), median nerve in midforearm (> 9.1 mm²), ulnar nerve in midupper arm (> 12.1 mm²), and tibial nerve 7 cm above medial malleolus (> 12.2 mm²) are useful screening points
- • Fibrolipomatous Hamartoma
Full access? Get Clinical Tree
