Useful biopsy results more likely
- Clinical features
- Clinical: Patient features
- Significant functional disability
- Higher yield
- Neuropathy is
Asymmetric.
- By history, examination, or electrodiagnosis
- Nerve is biopsied
- On more clinically affected side
- On side of smaller sural action potential
- Patient age > 65 years old
- Laboratory: Abnormal nerve conduction studies
- Neuropathy involves sensory loss
- Biopsy location: Nerve in region with clear sensory loss
- Sensory loss without weakness: Biopsy less likely to be useful
- Evaluation strategy: Specific diagnoses are sought.
- Surgery
- An experienced surgeon should perform the biopsy
- Sural nerves can be: Hard to find; Easy to damage
- Biopsy whole nerve (rather than few fascicles): Allows evaluation of
- Large vessels
- Epineurial connective tissue
- Comparative features of different fascicles
- Immune features
- Muscle: Biopsy at the same time
- Increased yield of immune, vascular & amyloid pathology
- Nerve biopsy specimens: Preparation
- Size
- Full thickness
- Length: > 3 cm
- Fresh: Transported in moist gauze on wood stick
- Processed: 3 pieces of equal size
- Frozen
- Formalin fixed: 10% Buffered Formalin
- Glutaraldehyde fixed
- Modified Karnovsky's Fixative
(3% Glutaraldehyde, 1% Paraformaldehyde in 0.1M sodium cacodylate)
- Nerve biopsies: Staining
- Nerve analysis
- Nerve is viewed in several preparations
- Frozen sections
- Paraffin embedded tissue
- Plastic sections: Toluidine blue stained
- Teased fibers
- Main value: Distinguish axonal from demyelinating pathology.
- Little diagnostic utility
- Ultrastructural analysis is available
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