Specimen Submission Guidelines for Pathologic Evaluation of CNS Infections

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Histopathologic changes in tissues and the pathogens that cause acute meningitis or encephalomyelitis may be distributed focally or sparsely in the central nervous system, and the predilection site for infection may vary among different organisms. Collecting multiple representative portions of CNS tissue, as well as tissue samples from any other organ system with inflammatory cell infiltrates, ensures the best chance of detecting the causative agent.

Performance of specific immunohistochemical, molecular, or other assays will be determined using clinical and epidemiologic information provided by the submitter and the histopathologic features identified in the submitted tissue specimens.

Collection of Tissue Specimens

The preferred specimens include paraffin blocks of involved CNS tissue, or representative tissues in formalin (i.e., wet tissue). Representative tissue specimens from each of the following sites should be obtained and submitted for evaluation:

  1. Cerebral cortex (frontal, parietal, temporal, and occipital)
  2. Brain stem (midbrain, pons, medulla) and spinal cord
  3. Cerebellum
  4. Basal ganglia, thalamus, hypothalamus, and hippocampus
  5. Meninges

If meningitis or encephalitis is identified in the context of a systemic illness (e.g., possible meningococcemia), representative tissues should be included from any other organ showing significant microscopic pathology.

Submission of Specimens

Paraffin-embedded tissue blocks

In general, this is the preferred specimen and is especially important to submit in cases where tissues have been in formalin for a significant time. Prolonged fixation (>2 weeks) may interfere with some immunohistochemical and molecular diagnostic assays.

Wet tissue

If available, we highly recommend that unprocessed tissues in 10% neutral buffered formalin be submitted in addition to paraffin blocks. The volume of formalin used to fix tissues should be 10x the volume of tissue. Place tissue collected according to the dimensions provided above in 10% buffered formalin for at least three days (72 hours) for biopsies, and 2 weeks for thinly-sliced autopsy tissues. After fixation, if not paraffin-embedded, tissues SHOULD be transferred to 70% ethanol for long term storage and for shipping.

Electron Microscopy (EM) specimens

Samples fixed in glutaraldehyde and held in phosphate buffer are needed. Sample containers should be filled to the top with phosphate buffer and sent on wet ice.  Do not freeze.  Epoxy-embedded tissues are also accepted.

Please refer to our General Guidelines for Submitting Pathology Specimens.