Nerve Biopsy

Home, Search, Index, Links, Pathology, Molecules, Syndromes,
Muscle, NMJ, Nerve, Spinal, Ataxia, Antibody & Biopsy, Patient Info

NERVE BIOPSY

Useful biopsy results more likely

Clinical features
- Clinical: Patient features
  - The neuropathy is asymmetric.
    - By history, examination, or electrodiagnosis
    - Nerve on the more clinically affected side is biopsied
    - Nerve is biopsied on the side of the smaller sural action potential
  - The neuropathy involves sensory loss.
    - Nerve in region with prominent sensory loss is biopsied
  - Patient age > 65 years old
  - Significant functional disability
    - Weakness
    - Sensory loss
- Evaluation strategy: Specific diagnoses are sought.
- Laboratory: Abnormal nerve conduction studies
Surgery
- An experienced surgeon should perform the biopsy
  - Sural nerves can be: Hard to find; Easy to damage
- The whole sural nerve is biopsied (rather than only 1 fascicle).
- Muscle is biopsied at the same time.
Nerve analysis
- The nerve is viewed in frozen or paraffin embedded, and in plastic, sections.
- Teased fibers
  - Main value: Distinguish axonal from demyelinating pathology.
  - Little diagnostic utility
- Ultrastructural analysis is available

Inflammatory
- Vasculitis: Inflammation; Differential fascicular involvement; Edema
- Perineuritis
Demyelinating Disorders
- Immune: CIDP
- Hereditary: Metachromatic Leukodystrophy (MLD)
Hereditary Disorders
- Giant Axonal Neuropathy
- Multi-Infarct dementia (CADASIL)
- Neuroaxonal Dystrophy
- CMT
  - General
  - Tomaculous neuropathies: HMSN, especially HNPP; CMT 4B
  - CMT 4C
- Metabolic disorders with distinctive changes & storage inclusions
Systemic Disease: Leprosy; Amyloid; Sarcoid
Toxic (with characteristic features, e.g. amiodarone)

BIOPSY FINDINGS IN NEUROPATHY

Morphologic changes in nerve or muscle with limited Differential diagnoses

Other nerve pathology

Other pathology in neuropathy: Denervation of muscle

Neurofilament accumulations in neuropathy

SMI 31 antibody

Sural nerve axons (Normal): Neurofilament stain

Mitochondrial abnormalities in neuropathy

Polyglucosan bodies

Tomaculae ¹

Features
- Myelin sheath
  - Focal folding (Redundant loops) or Thickening
  - Structure often disrupted: Splitting; Vacuoles
- Tomaculae distribution
  - Present on all sizes of myelinated axons
  - Several may occur in one internode
- Associated axon pathology: Small diameter; Dense axoplasm
- Other axons in same nerve: Often hypomyelinated; Fewer large diameter axons
Possible causes
- Hypermyelination
- Redundant myelin loop formation
- 2nd mesaxon
- Transnodal myelination
- Myelin sheath formed by 2 Schwann cells
General electrophysiologic correlations
- Multiple mononeuropathy
- Sensory + Motor involvement
- Demyelination
Diagnoses & Features of tomaculae
- Hereditary
  - PMP-22 mutations
    - HNPP: Common (50% of fibers); Very long (83 μm); Large diameter (16 μm)
    - CMT 1A: Occasional (10% to 30% of fibers); Very long (77 μm); Moderate diameter (14 μm)
    - Point mutations (Asp37Val; Gly94fsX222)
  - P₀ mutations
    - HMSN3 (Dejerine-Sottas): Numerous; Small
    - Entrapment neuropathies
  - CMT 4B1 (MTMR2): Very common (100% of fibers); Long (44 μm); Small diameter (11 μm)
  - CMT 4B2 (SBF2; MTMR13)
  - CMT 4E (EGR2)
  - CMT 4F (Periaxin)
  - CMT 4H (FGD4)
  - Juvenile glaucoma
- Immune
  - Anti-MAG neuropathy: Common (50% of fibers); Long (46 μm); Moderate diameter (14 μm)
  - CIDP: Occasional (13% of fibers); Long (56 μm); Large diameter (19 μm)
- Mouse model: PTEN disruption in Schwann cells
Pathology

Diseases

Cellular infiltrates in nerve: Inferences from cell types & location

Other pathological features of immune or inflammatory neuropathies

Return to Neuromuscular Home Page
Return to Normal nerve
Return to Biopsy illustrations
Return to Polyneuropathy Index

References
1. JNNP 2000;68:483-488

9/26/2011