When is Brain Biopsy Indicated?
April 1, 2012 4 minutes read
When is Brain Biopsy Indicated?
Abstract & Commentary
By Joseph E. Safdieh, MD, Assistant Professor of Neurology, Weill Cornell Medical College. Dr. Safdieh reports no financial relationships relevant to this field of study.
Synopsis: When a brain biopsy is being considered for a nonmalignant condition, the patients and the site of biopsy must be carefully selected to ensure the most useful results.
Source: Gilkes CE, et al. Brain biopsy in benign neurological disease. J Neurol 2012 DOI 10.1007/s00415-012-6455-0.
Brain biopsy is an established tool in clinical prac- tice in the diagnosis of brain tumors. However, a number of brain biopsies are performed to diagnose nonmalignant conditions. That said, the role of brain biopsy in nonmalignant conditions is less certain and has not been well defined. Biopsies can be helpful in cases of CNS lesions in immunosuppressed patients, undiagnosed dementias, angiogram-negative cerebral vasculitis, prion diseases, and other cryptogenic neurological diseases. There are no published guidelines regarding the selection of the proper patient, or timing or location of biopsies, and biopsy policies differ significantly between academic medical centers.
Gilkes et al provide a review of the literature, summarizing the experience with brain biopsies for nonmalignant conditions at different institutions. The study periods ranged from 1998 through 2008, with the number of biopsies ranging from 39 to 68. A histological diagnosis was made in 29-65% of biopsies. The most common diagnoses were demyelination, Creutzfeldt-Jakob disease, vasculitis, and lymphoma. Complication rates ranged from 4-11%. The authors point out that both diagnostic biopsies as well as nondiagnostic biopsies can influence management, since nondiagnostic biopsies may rule out certain conditions that might have required potentially toxic therapies.
In patients with undiagnosed neurological disease, the indications for biopsy include establishing a diagnosis before initiating disease-specific therapy, providing diagnostic support in the case of rapid neurological decline, and diagnosing a prion disease. The varying diagnoses described at differing sites reflect, to some extent, a selection bias in patient referral as well as practice variations regarding which patients are actually biopsied. Additionally, the handling of the specimen and types of stains performed may differ by site, thereby contributing to the variability seen in the literature.
Before a brain biopsy is considered, it is important to exclude diagnoses that can be made by other less invasive means. This includes, in appropriate cases, testing for HIV, autoimmune and paraneoplastic encephalopathies, very long chain fatty acids, white cell enzymes and metabolic screening, CSF analysis with viral PCRs, electrodiagnostic studies, cerebral angiography, bone marrow biopsy, and biopsies of other organs or non-neurologic lesions such as skin, muscle, nerve, GI tract, or tonsil. There are many recently described paraneoplastic diseases, including NMDA-receptor encephalitis, and these should be excluded before biopsy. Of course, the clinical presentation should guide the appropriate tests.
Commentary
Most brain biopsies are performed via burr hole or small craniotomy and should include 1 cubic centimeter of tissue, including gray matter, white matter, and meninges. It is important to include meninges because certain conditions like CADASIL and other microangiopathies might be missed otherwise. The radiology should guide the location of the biopsy, and the biopsy should be taken from tissue that is abnormal on imaging, especially in areas that demonstrate gadolinium enhancement. However, in some cases, if the imaging does not have a specific lesion, it is standard to take tissue from the nondominant frontal lobe. The risk of brain biopsy is generally low, with modern studies reporting a complication rate of 4-8%, mostly transient side effects, and in the authors' series there were no deaths or hemorrhages reported.
It is important that the neurosurgeon, neuroradiologist, and neuropathologist are all fully informed regarding the differential diagnosis that is being considered in the selected patient, and the authors suggest that at least two neurologists consult independently on the patient to exclude conditions that can be diagnosed without biopsy. Most brain biopsies are performed after preservation in formalin but it is important that fresh tissue be sent as well for microbiological analysis and genetic analysis and that some tissue be saved for electron microscopy. The authors also recommend that frozen tissue be stored for repeat analysis at a later date pending the emergence of new information or new technologies.
The authors present an algorithm for considering brain biopsy, which includes making sure the patient has an undiagnosed condition after appropriate less invasive testing, review of the clinical condition and neuroimaging by a qualified neuroradiologist, at least two neurologists performing a preoperative consultation with a neurosurgeon to make sure the biopsy site is agreed upon and tissue handling is done properly, and preoperative consultation with the neuropathologist to ensure proper stains are done. Proper communication between the various services is likely the most important step in obtaining the most helpful biopsy result.
When a brain biopsy is being considered for a nonmalignant condition, the patients and the site of biopsy must be carefully selected to ensure the most useful results.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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