Imaging Modalities: Neuropathology

Abstract

Neuropathology is the medical discipline concerned with the study of diseases affecting the central and peripheral nervous system as well as muscle. Its aim is to describe the structural, biochemical, molecular, and functional changes in the various cells which make up the nervous system. Using morphologic, immunologic, and molecular biological techniques, neuropathology tries to explain the signs and symptoms of patients. Delivering a clear-cut diagnosis provides the rational basis for patient care and therapy. Specimens for analysis are obtained through autopsy (brain, spinal cord, meninges), open brain surgery, biopsy (stereotactic or navigated biopsy, muscle and nerve biopsy), and lumbar puncture. The procedures for removal, fixation, and cutting of the brain and spinal cord, fixation and processing of tissue are crucial in the analysis pipeline. Staining techniques for tissue received in the neuropathology laboratory include classical stains (Hematoxylin and Eosin (H&E)), special stains (Periodic acid-Schiff (PAS)), diastase-sensitive PAS or PAS with diastase digestion, Alcian blue), and special stains for connective tissue. Special neuro-stains include cresyl violet (Nissl stain), Luxol fast blue (LFB), phosphotungstic acid hematoxylin (PTAH), modified Bielschowsky, and Gallyas stain. The principles of immunohistochemistry are described and supplemented by short characterization of markers for neurons, synapses, astroglia, oligodendroglia, myelin, microglia, neurodegeneration, tumors, vessels, hematopoietic and lymphatic cells, proliferation markers in tumors, and markers for infectious agents. Immunohistochemical panels for the diagnostic setting are provided. Other techniques used in neuropathology comprise electron microscopy, fluorescence microscopy, enzyme histochemistry, and in situ hybridization (ISH). Molecular biology techniques as used in neuropathology include blot techniques (Western blot to visualize proteins, Northern blot to visualize RNA, Southern blot to visualize DNA, Dot blot), molecular imaging with imaging a mutation after sequencing and imaging a deletion, duplication with RT-PCR as well as microarray techniques. Other imaging techniques, developed during the last decades, include Confocal Laser Scanning Microscopy, Multiphoton Confocal Fluorescence Microscopy, Atomic Force Microscopy (AFM), and many others.