Test Catalog

Test ID: PNBX    
Peripheral Nerve Pathology Consultation

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluating diseases of the nerve and disorders that affect nerve function

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

A battery of enzyme histochemical stains or immunostains are performed; other tests can be performed as indicated at an additional charge. The reviewing neuromuscular pathologist will determine the need for additional testing.


Wet tissue for consultation: When adequate tissue is provided, routine testing will include: teased fiber examination, Congo red stain, Turnbull blue stain, methyl violet stain, Masson's trichrome stain, leukocyte common antigen, luxol fast blue/PAS stain, KP-1 macrophage, methylene blue stain, and hematoxylin and eosin stain.


Slides and blocks sent for consultation: Special stains and studies performed on the case should be sent with the case for review. In order to determine an accurate diagnosis, some of these stains or studies may be deemed to warrant repeat testing, at an additional charge, at the discretion of the reviewing Mayo Clinic neuromuscular pathologist. In addition, testing requested by the referring physician (immunostains, molecular studies, etc) may not be performed if deemed unnecessary by the reviewing Mayo Clinic neuromuscular pathologist. For all consultations, ancillary testing necessary to determine a diagnosis is ordered at the discretion of the Mayo Clinic neuromuscular pathologist. An interpretation, which includes an evaluation of the specimen and determination of a diagnosis, will be provided within a formal pathology report.


See Pathology Consultation Ordering Algorithm in Special Instructions.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Nerve biopsies provide information about nerve fibers and the interstitium of the nerve. Neuropathic abnormalities include decreased density of myelinated fibers, segmental demyelination, and axonal degeneration. Some possible interstitial abnormalities that affect nerves include necrotizing vasculitis and amyloidosis.


This consultation is for fixed tissue, slides, or blocks.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

The clinical and neurological history is reviewed with the interpretation of the biopsy.


The histologic slides, special stains, and history, along with the physician's report are correlated by a neuromuscular pathologist. An interpretive report will be provided.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Poor fixation, orientation, and improper handling of the nerve tissue may hinder the neuromuscular pathologist's interpretation of the biopsy. See directions for Nerve Biopsy Specimen Preparation in Special Instructions. Kits containing the proper tissue fixatives and buffers are available upon request.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Tracy JA, Dyck PJ, Klein CJ, Engelstad JK, Meyer JE, Dyck PJB: Onion-bulb patterns predict acquired or inherited demyelinating polyneuropathy. Muscle Nerve. 2019 Jun;59(6):665-670

2. Xu M, Pinto M, Sun C, et al: Expanded teased nerve fibre pathological conditions in disease association. J Neurol Neurosurg Psychiatry. 2019 Feb;90(2):138-140

3. Dyck PJB, Spinner RJ, Amrami KK, Klein CJ, Engelstad JK, Dyck PJ: MRI-targeted fascicular nerve biopsies of proximal nerves: historic reports and illustrative case reports. In: Dyck PJ, Dyck PJB, Engelstad JK, et al, eds. Companion to Peripheral Neuropathy: Illustrated Cases and New Developments. Elsevier; 2010:3-14

4. Dyck PJ, Dyck PJB, Engelstad J: Pathologic alterations of nerves. In: Dyck PJ, Thomas PK, eds. Peripheral Neuropathy, Vol. 1. 4th ed. Elsevier; 2005:733-829

Special Instructions Library of PDFs including pertinent information and forms related to the test