Brain biopsy

neurosurgery

1. Brain Biopsy Payoz

2. Introduction It is used to determine the cause of diffuse or multifocal diseases producing minimal mass effect when the specific diagnosis cannot be established by any other means Studies assessing the usefulness and risks of brain biopsy began in 1950(Queen square study) and was initially focused on 3 main areas namely Paediatric Neurodegenrative diseases,viral encephalitis and dementia. With advent of modern techniques for confirming conditions,indications for brain biopsies have reduced markedly.

3. Criterias for Brain Biopsy 1) No alternate procedure can provide the diagnosis 2) The information from biopsy will serve a useful purpose

4. Indications Infections Vasculitides Paediatric neurodegenerative diseases dementia

5. Infections Herpes simplex encephalitis although the diagnosis can be made on clinical and radiological evidence there are certain factors that favour a biopsy namely Only patients with infections due to herpes simplex and varicella zoster would benefit from acyclovir therapy It fairly commonly detects superadded bacterial or fungal infections which require an entirely different therapy

6. Acquired immune deficiency syndrome CT and MRI is commonly unable to distinguish the various CNS manifestations of AIDS(toxoplasmosis vs lymphoma vs progressive multifocal leukoencephalopathy ) Definitive diagnosis of certain Bacterial and Fungal infections mucormycosis , aspergillosis , nocardiosis and rare cases of actinomycosis require biopsy for confirmation and appropriate treatment. Chronic inflammatory conditions like lyme neuroborreliosis

7. Vasculitides May present with multifocal symptoms and normal laboratory studies May not even be visible on MRI or CT studies and requires biopsy on clinical suspicion . It is recommended to take biopsy from temporal tip including area of longitudinally arranged surface vessels

8. Paediatric Neurodegenerative Disease Majority of the cases can be diagnosed with Radiological ,biochemical and genetic studies. Two condition that require biopsy for differentiation are- Canavan’s disease and Alexander’s disease.

9. Canavans Disease Characterised by psychomotor retardation, macrocephaly and spasticity . MRI shows high intensity signals in T2 weighted images. This is an autosomal recessive condition and definitive diagnosis is necessary for counselling. Brain biopsy specimen shows intramyelenic vacuolation in the subcortical white matter and swollen astrocytes with abnormal mitochondria in deeper layers of the cortex

10. Alexanders disease Sporadic Unknown etiology Presents in infancy with psychomotor retardation ,progressive enlargement of head and spasticity. Biopsy demonstrates Rosenthal fibres in subpial ,perivascular and subependymal locations No available treatment

11. Dementias Brain Biopsy is used in diagnosis of atypical dementias and rare forms of dementia.

12. Incidental Biopsy It is incidental sampling of tissue at time of other operation e.g removal of brain tissue/meninges at time of evacuation of haematoma , resection of neoplasm etc.

13. Team approach Brain biopsy should be preceded by discussions among the individual requesting the biopsy, performing the biopsy and the one examining the biopsy specimen. This will help determine the appropriate site of biopsy and chosing the best microbiological,morphological and neurochemical studies. When possible the biopsy should be performed during the normal working hours when a full complement of qualified technical personnel are available to initiate various lab studies

14. Surgical technique The procedure must be planned and executed with the ususal attention to anaesthetic technique, positioning , skin preparation and draping, surgical technique and dressing Pre-operative antibiotic and anticonvulsant medication should be given Drugs that alter sensorium should be minimized post -operatively

15. Anaesthesia and Medication General endotracheal anaesthesia is used most commonly, but if patient is co-operative biopsies can be taken under light sedation and local anaesthesia If Raised ICP is a factor, Mannitol and hyperventilation should be utilised

16. Operative Technique For a temporal Lobe biopsy, Patient is positioned supine and GA is induced. With doughnut pad under the head, the head is turned to the side at a level above the heart and a towel roll is placed under the shoulder. A small area of scalp is shaved and operative site prepared . A 5 cm curvilinear incision is drawn 1 cm anterior to the external auditory meatus which extends up to the zygoma and turns posteriorly above the ear to approximately 1 cm above the pinna The region is draped with paper drapes and a betadine impregnated adhesive plastic sheet placed.

17. The propsed incision site is infiltrated with 0.5-1% lidocaine with 1:100000 epinephrine. The incision is carried to the peri-osteum and the bone is cleared. Retraction is maintained with the Weitlaner retractor. A burrhole is made. (In awake patients, power drills are unncesarily loud and potentially frightening hence avoided). The Hole is enlarged to 2-2.5 cm with roungeurs . The Dura is opened in a cruciate or curvilinear fashion. Using a no 11 blade, the brain is incised in a square large enough to obtain sufficient material for all the studies needed, generally 1-1.5 cm on each side and 1.5 cm deep, and including grey and white matter and its sulcus. The tissue is undermined with a dissector and lifted free with a cuffed foreceps . After haemostasis is obtained, a routine closure is carried out.

18. Tissue for viral and other cultures should be immediately placed in sterile containers to avoid contamination. Stereotactic craniotomy may be indicated to improve localization and minimize the site of opening

19. Post-operative complications Haematoma formation Brain swelling Neurological deterioration Focal neurological deficits Seizures Infections Medical complications death

20. Thanks