Background

The nervous system has traditionally been divided into the central nervous system which includes the brain and spinal cord, and the peripheral nervous system which consists of all other nerves besides the twelve cranial nerves. Obviously, the distinction is artificial since one is connected with the other.   The peripheral nervous system interfaces with skeletal muscle at the neuromuscular junction. Skeletal muscle biopsies involve specialized processing with fresh tissue frozen immediately for specialized enzyme studies.  In addition, a small sample is submitted for electron microscopic study.  Finally, a portion is submitted for routine and special stains.  Pathologists specializing in disorders of the neuromuscular system are called neuropathologists. They must have an accurate knowledge base of clinical neurology and neurosurgery as well as mastery of pathology.  

• Guillain-Barre Syndrome
• Myasthenia Gravis
• Mitochondrial Myopathies
• Myopathy Differential Diagnosis

OUTLINE

Epidemiology
Disease Associations
Pathogenesis
Laboratory/Radiologic/ Other Diagnostic Testing
Gross Appearance and Clinical Variants
Histopathological Features and Variants
Special Stains/ Immunohistochemistry/ Electron Microscopy
Differential Diagnosis
Prognosis
Treatment
Commonly Used Terms
Internet Links

HISTOPATHOLOGY	CHARACTERIZATION
FINE NEEDLE ASPIRATION
Comparison of needle core biopsy and fine-needle aspiration for diagnostic accuracy in musculoskeletal lesions. Yang YJ, Damron TA. Department of Pathology, Upstate Medical University, State University of New York, Syracuse, NY, USA	Arch Pathol Lab Med. 2004 Jul;128(7):759-64. Abstract quote CONTEXT: Needle core biopsy has been reported to be the choice of biopsy for musculoskeletal tumors. Fine-needle aspiration, on the other hand, has been widely accepted for nonmusculoskeletal tumors, but is only used in selected medical centers for musculoskeletal tumors. While fine-needle aspiration appears to have advantages to needle core biopsy in the aspects of simplicity and cost, the diagnostic accuracy should be the most critical parameter in determining the choice of biopsy. However, few studies comparing the diagnostic accuracy of these 2 biopsy methods have been performed. OBJECTIVE: This study was designed to compare the diagnostic accuracy of fine-needle aspiration and needle core biopsy in musculoskeletal tumors. DESIGN: Prospective study was performed in patients aged 10 years or older. Diagnostic accuracy was compared in 50 consecutive concurrent needle core biopsies and fine-needle aspirations of musculoskeletal lesions. RESULTS: For primary musculoskeletal lesions, fine-needle aspiration achieved a diagnostic accuracy rate of 88% for nature of lesion, 64% for specific diagnosis, 78% for histologic grading, and 74% for histologic typing. Needle core biopsy achieved an accuracy rate of 93% for nature of lesions, 83% for specific diagnosis, 83% for histologic grading, and 90% for histologic typing. Both biopsy methods have a higher diagnostic accuracy rate for high-grade tumors than for low-grade or benign lesions in determining the nature, specific diagnosis, and histologic grading. CONCLUSIONS: The needle core biopsy has a higher diagnostic accuracy than fine-needle aspiration in all aspects, including determining the nature of the tumor, establishing the histologic type and grade, and achieving a specific diagnosis.
VARIANTS
TRAUMA
Cutaneous sensory nerve fibers are decreased in number after peripheral and central nerve damage Joanna Wallengren, MD, PhD Eva Tegner, MD, PhD Frank Sundler, PhD Lund, Sweden	J Am Acad Dermatol 2002;46:215-7 Abstract quote Two dermatologic patients displaying peripheral and central nerve damage, respectively, are described. Cutaneous nerve fibers in both patients were studied in skin biopsy specimens taken from neuropathic areas and from the contralateral side, immunocytochemistry being applied to a pan-neuronal marker, a protein gene-product (PGP 9.5). One of the patients, suffering from compression of the ulnar nerve, had dyshidrotic eczema of the hands that was absent on areas of skin that were neuropathic. The cutaneous innervation (most of which was sensory) was reduced by 50% in the neuropathic area as compared with the contralateral side. The other patient had unilateral pruritus on the parethic side after a stroke. The cutaneous innervation of that side was reduced by 80% as compared with the other side. It seems that peripheral sensory innervation is a prerequisite for inflammation, whereas spontaneous itching may emanate from a central nervous system disorder such as a stroke and continue on in partly denervated skin.

 

SPECIAL STAINS/ IMMUNO-HISTOCHEMISTRY

CHARACTERIZATION

Ubiquitin immunostaining and inclusion body myositis: study of 30 patients with inclusion body myositis. Prayson RA, Cohen ML. Department of Pathology, Cleveland Clinic Foundation, and Case Western Reserve University, OH 44195, USA.

Hum Pathol 1997 Aug;28(8):887-92 Abstract quote Distinction of inclusion body myositis (IBM) from other forms of inflammatory myopathy is significant from prognostic and therapeutic standpoints. This study retrospectively examines ubiquitin expression by paraffin immunohistochemistry in muscle biopsy material from 30 patients with IBM. Patients included 19 men and 11 women (ages 29 to 80 years; mean, 64 years). All biopsies were characterized by endomysial chronic inflammation, muscle fiber degeneration and regeneration, rimmed vacuoles, and angular atrophic esterase-positive muscle fibers. Ragged red fibers were identified in biopsies of five patients and a partial cytochrome C-oxidase deficiency by enzyme histochemistry in biopsies of 10 patients. Evidence of intranuclear or cytoplasmic tubulofilamentous structures confirming a diagnosis of IBM was observed in all 30 cases. Paracrystalline mitochondrial inclusions were noted in five patients. Discrete myocyte intranuclear ubiquitin-positive inclusions were noted in 14 patients (47%). Discrete intracytoplasmic ubiquitin-positive inclusions were noted in 24 (80%) patients. Positive staining of rimmed vacuoles by ubiquitin was observed in 25 (83%) patients. Diffuse staining of scattered muscle fibers was observed in 21 (70%) patients. In a control group including patients with polymyositis (n = 3), dermatomyositis (n = 3), necrotizing vasculitis (n = 1), and granulomatous myositis (n = 1), discrete intranuclear or cytoplasmic ubiquitin-positive inclusions were not observed. Rimmed vacuoles were not seen either by light microscopy or ubiquitin immunostaining in any of the eight cases. Occasional myofibers from all eight cases showed diffuse, positive muscle fiber staining. Although not present in all cases, evidence of ubiquitin-positive myocytic intranuclear or cytoplasmic inclusions or positive-staining rimmed vacuoles in the setting of an inflammatory myopathy may be suggestive of a diagnosis of inclusion body myositis. Use of ubiquitin immunohistochemistry may be useful in cases in which frozen tissue or tissue processed for electron microscopy is not available, and IBM is suspected. Light or electron microscopic evidence of mitochondrial abnormalities were noted in a significant subset of patients (13 of 30; 43%) of patients with IBM.

Rosai J. Ackerman's Surgical Pathology. Eight Edition. Mosby 1996.
Sternberg S. Diagnostic Surgical Pathology. Third Edition. Lipincott Williams and Wilkins 1999.
Robbins Pathologic Basis of Disease. Sixth Edition. WB Saunders 1999.

Demyelination-Loss of myelin.

Gliosis-Benign and reactive proliferation of glial cells comprised predominately of astrocytes and oligodendrocytes.

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Last Updated 7/1/2004

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