Canis ISSN: 2398-2942

Biopsy: brain

Contributor(s): Sam Long, Simon Platt

Introduction

  • Advent of intracranial imaging has led to rapid advances in the diagnosis of intracranial lesions.
  • CT and MRI scanning help localize but often leave a list of differentials for any given lesion including neoplasia, inflammation and infection.
  • It is important to obtain precise diagnosis for optimal treatment which may require sampling lesions via conventional surgical techniques or through more specialized stereotactic needle biopsy systems.

Stereotactic biopsy systems

  • Used for locating and sampling points within the brain using an external, 3 dimensional frame of reference.
    • Used first 1947 for biopsy of intracranial lesions in humans. Advanced imaging has led to image guided stereotactic biopsy.
    • Minimally invasive and associated with low morbidity. Overall complication rates varying between 2-6% and with mortality rates of between 0-2.3% (Kondziolka Det al1998).
    • Recently developed for use in animals for diagnosis of intracranial lesions but not yet widely available. Overall morbidity and mortality rates higher than man; dogs (12-26%) and cats (7-8%) (Koblik P Det al1999).

Pathological techniques aid intra-operative diagnosis

  • Two-fold aims:
    • To confirm the diagnostic value of a specimen and to minimize number of specimens taken.
    • To provide provisional histopathologic diagnosis to aid management decisions in early postoperative period.
  • Some methods require equipment and training not accessible to many veterinarians, in addition to specialist anesthesia assistance; other methods are simple and rapid to perform and may yield valuable information.

 

Uses

  • Brain lesions biopsied for one of three reasons:
    • To provide diagnosis for optimal treatment.
    • To provide diagnosis for more accurate prognosis.
    • As part of therapy (either excisional biopsy in an attempt to cure disease, cytoreduction for subsequent radiotherapy or debulking to alleviate mass effect and clinical signs).
  • Investigation of patient with intracranial disease may give clinician information regarding location and size of the lesion, if visible on imaging studies. However, even after ancillary tests such as CSF taps, serological tests and EEG are performed, the differential list may include diseases that require very different therapeutic approaches. Therefore, definitive diagnosis and therapy may require biopsy of the lesion involved.
  • Different lesions may be more suited to either conventional intracranial surgical biopsy or stereotactic or needle biopsy (see decision taking).
  • Lesions that are most suited to stereotactic or needle biopsy are easily visible on imaging studies, especially following contrast administration.
  • Biopsy may aid the diagnosis of focal lesions such as the focal form of granulomatous meningoencephalitis (GME) Granulomatous meningoencephalomyelitis , abscesses, localized encephalitis/meningitis Encephalitis and most tumors Brain: neoplasia.
  • Lesions less suited to stereotactic or needle biopsy are those that are diffuse in nature such as diffuse tumors, eg gliomatosis cerebri and some lymphomas, diffuse GME and viral encephalitides as selection of representative areas for sampling becomes more challenging Brain biopsy 01: intraparenchymal hemorrhage CT.
  • Once decision is made to perform biopsy, several techniques are available to allow an intraoperative diagnosis to be made which provide useful information until conventional processing and histological examination results are ready.
  • Frozen cryostat preparation is the most common method that allows for examination of larger amounts of material and thus is likely to give a more accurate picture of the lesion. However, this requires approximately 30 minutes processing time and is only possible if facilities for rapid freezing and frozen sectioning are available.
  • Crush or smear technique is a cytological technique that allows for rapid examination of tissue (approx 90 seconds). Uses less tissue thus leaving more tissue to be submitted for conventional histopathology but may provide less accurate diagnosis, eg smear biopsy analysis may confirm a diagnosis of neoplasia but not definitively confirm the grade of malignancy.

Advantages

Conventional biopsy (via open craniotomy) Advantages and disadvantages of brain biopsy methods

  • Procedure allows for decompression in patients suffering from raised intracranial pressure by removing tumor bulk.
  • Cytoreduction.
  • Allows control of hemorrhage during surgery in patients with highly vascular lesions, ie vascular tumors such as choroid plexus tumors.
  • Can be used to perform needle biopsy using ultrasound guidance for deeper lesions. This technique provides some relief of intracranial pressure while enabling a diagnosis to be made, but does not allow for debulking or control of hemorrhage intraoperatively.

Stereotactic biopsy

  • Allows access to deeper parts of the brain, such as deep gray matter of forebrain and brainstem.
  • More conventional fine needle aspirates Fine-needle aspirate through a small burr hole drilled in skull can be used for very superficial lesions in addition to stereotactic biopsy techniques.
  • Associated with lower morbidity and mortality since causes less trauma to brain tissue.

Disadvantages

Conventional biopsy (via open craniotomy) Advantages and disadvantages of brain biopsy methods

  • Only allows access to superficial parts of the brain:
    • The rostral, dorsal and lateral parts of the cerebral hemispheres and parts of the cerebellum.
  • Lesions in the deep gray matter of forebrain or within brainstem are not accessible.

Stereotactic biopsy

  • Does not allow for decompression, either in patients with raised intracranial pressure before surgery or in patients who suffer hemorrhage and subsequent expansion of the lesion following surgery.
  • Yields smaller amount of tissue than open biopsy leading to non-diagnostic samples if a representative part of lesion is not sampled.
  • As availability of stereotactic frames is limited, the learning curve associated with their initial use is likely to be steep, and the time necessary for the biopsy procedure longer than conventional craniotomy. However, with experience these factors are likely to become less significant.
  • CT or other imaging studies used to localize region to be biopsied.
  • Need CT Computed tomography or MRI Magnetic resonance imaging: brain compatible equipment.

Requirements

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Procedure

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Aftercare

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Giroux A, Jones J C, Bøhn J H et al (2002) A New Device for Stereotactic CT-guided biopsy of the canine brain: design, construction and needle placement accuracy. Vet Radiol & Ultra 43 (3), 229-236 PubMed.
  • Long S N, Anderson T J, Long F H et al (2002) Evaluation of rapid staining techniques for cytologic diagnosis of intracranial lesions. Am J Vet Res 63 (3), 381-386 PubMed.
  • Moissonnier P, Blot S, Devauchelle P et al (2002) Stereotactic CT-guided brain biopsy in the dog. JSAP 43 (3), 115-123 PubMed.
  • Platt SR, Alleman A R, Lanz O I et al (2002) Comparison of fine-needle aspiration and surgical-tissue biopsy in the diagnosis of canine brain tumors. Vet Surg 31 (1), 65-69 PubMed.
  • Vernau K M, Higgins R J, Bollen A W et al (2001) Primary canine and feline nervous system tumors: intraoperative diagnosis using the smear technique. Vet Pathol 38 (1), 47-57 PubMed.
  • Spugnini E P, Thrall D E, Price G S et al (2000) Primary irradiation of canine intracranial masses. Vet Radiol Ultrasound 41 (4), 377-80 PubMed.
  • Koblik P D, LeCouteur R A, Higgins R J et al (1999) Modification and application of a Pelorus Mark III stereotactic system for CT-guided brain biopsy in 50 dogs. Veterinary Radiology & Ultrasound 40 (5), 424-433 PubMed.
  • Koblik P D, LeCouteur R A, Higgins R J et al (1999) CT-guided brain biopsy using a modified pelorus Mark III stereotactic system: experience with 50 dogs. Veterinary Radiology & Ultrasound 40 (5), 434-440 PubMed.
  • Kondziolka D, Firlik A D & Lunsford L D (1998) Complications of stereotactic brain surgery. Neurology Clinics 16 (1), 35-54 PubMed.

Other sources of information

  • Summers B A, Cumming J F & de Lahunta A (1995)Veterinary Neuropathology.St Louis, Mosby.


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