Neuropathology

A. Autopsy

1. Prior to starting the autopsy, determine, from the clinical history, the presences or absence of neurological manifestations.. This will help you to plan re: taking tissue for special studies, giving tissue for research, and in examining the brain and spinal cord for clinically relevant findings. (See section below for discussion of brain removal in cases with infections or other hazards.)
   
   

2. Brain removal, while generally done by the morgue attendant, should be learned by the resident as well.
   
   

3. Prior to fixation, weigh the brain:

   1. Look for evidence of meningeal infection and culture as needed. Look for abscess exposed to the brain's surface and culture as needed. Look at the base of the skull for evidence of meningiomas and sample and photograph.

   2. Consider whether the pituitary gland would be of diagnostic interest in your case.
      
      

4. The brain should be floated in 20% formalin, suspended by a string going under the basilar artery.
   
   

5. The brain must fix for 2 weeks in 20% formalin before it is cut. It must be rinsed for 24 hours prior to brain cutting conference.
   
   

6. There are standard description forms for both demented and non-demented patients.

7. Neuropathology brain cutting: Every week.

(Appendix XI)

B. Neuropathology Surgicals

1. Neuropathology surgical specimens (in-house, submitted) interpretation performed by the neuropathologist.

2. Frozen sections are done in consultation with the neuropathologist.

3. Nerve: The nerve should be received in saline moistened gauze, not in fixative!

Fresh peripheral nerve that is for a diagnosis of a neurologic illness (the excludes vagotomies) must be divided as follows:

One cm of nerve should be laid out on a piece of a 3x5 card and emmersed in glutaraldehyde to allow for both cross section and longitudinal section embedding for electron microscopy. An additional1 cm should be fixed in glutaraldehyde for nerve testing if demyelination is suspected. Two small pieces, approximately 0.3 cm each should be fixed in formalin for cross section and longitudinal section evaluation at the light microscope. A section of the nerve must be frozen if there is evaluation at the light microscope. A section of the nerve must be frozen if there is any suspicion of paraneoplastic disease, to allow for immunofluorescence for immunoglobulin depostition. See Appendix XXXI (pages from Dyck Peripheral Neuropathy on nerve biopsies)

4. Muscle and Fascia: The muscle should be receieved in a muscle clamp, fresh from surgery, without any fixative. It may be wrapped in saline moistened gauze until it is ready for processing. The muscle must then be divided for different methods of processing. The muscle inside the clamp (between the teeth) must be used for snap frozen section for histochemistry (dipped in isopentane, suspended in liquid nitrogen, on a cork base with a touch of OCT to hold it down--DO NOT COVER WITH OCT AS THIS WILL DELAY FREEZING). The muscle outside the clamp's teeth is to be used both for electron microscopy and paraffin embedding. This tissue can be divided with a few small pieces of unadulterated muscles going into glutaraldehyde (usually cut into pieces measuring 1x1x2mm each). A larger piece should be submitted for routine H&E staining and trichrome and should be sufficient to allow for embedding longitudinally and cross-section. The stains ordered routinely should include: H&E on both paraffin and frozen, On snap frozen tissue: Trichrome, ATPase at pH4.3 and 10.4, NADH, PAS, fat cytochrome C (and dystrophin for all patients less than 20 years of age). Cytochrome C and dystrophin are immunohistochemical stains, the remainder are histochemical (NAD & ATPase are enzyme histochemistry). See Appendix XXXI from Muscle Biopsy: A Laboratory Investigation by Mike Loughlin.

5. Pituitaries need only one H&E and one reticulin on each specimen submitted. If the tumor is grossly obvious, the immunohistochemical stains for the purported syndrome may be ordered at the time that the specimen is received, as follows:

   • Cushings syndrome - ACTH

   • Prolactinoma - prolactin

   • Acromegaly - growth hormone

   • Etc.

For technical preparation, see Surgical Pathology Section.