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ORIGINAL ARTICLE |
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| Year : 2009 | Volume
: 4
| Issue : 1 | Page : 17-19 |
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Transcerebellar stereotactic biopsy for brainstem lesions in children
Purav Patel, M Balamurugan
Department of Neurosurgery, Apollo Speciality Hospital, Chennai, India
Correspondence Address:
Purav Patel
Department of Neurosurgery, Apollo Speciality Hospital, Chennai
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/1817-1745.49101
 Abstract | | |
Brain stem lesions are pathologically heterogeneous. Pre-operative radiological diagnoses prove to be wrong in 10 to 20% of cases. It is therefore imperative to have a tissue diagnosis for appropriate therapeutic measures. We report a series of 24 patients (14 males, ten females, age range: 6-17 years) CT guided stereotactic biopsy for brain stem lesions approached via the suboccipital transcerebellar route in semi sitting position with principle used to violate only one pial plane with the biopsy probe not entering the ventral surface of the cerebellum. The inclusion and exclusion criteria with detailed material and method are discussed. Histological diagnosis was established in 23 patients (96%) with no procedure-related mortality. Our results indicate that stereotaxic approach to brain-stem lesions provides a high yield of positive histological diagnoses with a low incidence of morbidity. Awake CT-guided stereotactic biopsy via the suboccipital transcerebellar route in a semi-sitting position is a safe, reliable, and effective method for brainstem lesions that can obtain adequate tissue for histological diagnosis, thus providing each patient with the best available treatment.
Keywords: Brain stem lesions, stereotactic biopsy, transcerebellar, semi sitting position, awake biopsy
How to cite this article:
Patel P, Balamurugan M. Transcerebellar stereotactic biopsy for brainstem lesions in children. J Pediatr Neurosci 2009;4:17-9 |
| Introduction | |  |
Brain stem lesions are pathologically heterogeneous. [1],[2] Despite improved brain-stem imaging by magnetic resonance and high-resolution X-ray computerized tomography, preoperative radiological diagnoses prove to be wrong in 10-20% of all cases. [1],[3],[4] It is therefore imperative to have a tissue diagnosis to take appropriate therapeutic measures. [2],[4] Stereotactic biopsy of lesions in the brain stem has been performed since the 1960s. [1],[5],[6] We report here a series of 24 patients (14 males, ten females, age range: 6-17 years) who underwent CT-guided stereotactic biopsy for brain stem lesions by the suboccipital transcerebellar route in a semi-sitting position. Presented here is a detailed description of the transcerebellar approach used by the author and the significance and advantages of transcerebellar biopsy in the awake stage.
| Materials and Methods | | |
Presented herein is a series of 24 transcerebellar stereotaxic biopsy procedures performed on intrinsic lesions of the mesencephalon, pons, and the medulla from March 2004 to December 2007 at the Apollo Speciality Hospital, Chennai. Eleven patients had midbrain lesions, eight had pontine, and five had ponto-medullary lesions. Procedures were carried out using general endotracheal anesthesia in six patients (four males, two females, age range: 6-10 years) whereas biopsy was performed in the awake state in othe ther 18 patients (ten males, eight females, age range: 7-17 years).
The basic principle used was to violate only one pial plane with the biopsy probe not entering the ventral surface of the cerebellum in its path to avoid damage to vessels in that space.
Inclusion Criteria
- Lesions located in the dorsal midbrain, midbrain-pontine junction, midpontine / diffuse pontine region, and ponto-medullary junction.
- Lateralized lesions with infiltration of the cerebellar peduncle.
Exclusion Criteria
- Rostral midbrain lesions and lesion in the anterior part of the brainstem.
- Dorsallly exophytic lesions which underwent open surgery.
The CRW stereotactic head ring fixation (under local anesthesia nerve block) was done as low as possible on the head to ensure that the target was accessible. The anteroposterior angulation can be adjusted as per tumor size and biopsy site. The base ring was fixed to a specially made wooden board fixed to a stretcher [Figure 1A]. A contrast CT was done with the localizer ring fixed to the head ring with 2 mm cuts in the area of interest [Figure 1B].
The patients were positioned in a semi-sitting position [Figure 2A]. An entry point was chosen below the level of the transverse sinus at an appropriate distance lateral to the midline to enable access to the tumor and to avoid vascular structures [Figure 2C]. The computerized tomography and magnetic resonance imaging were helpful in trajectory selection.
Keeping the patient awake [Figure 2B] and clinically monitoring the procedure allowed us to make the necessary changes in the trajectory of the biopsy probe to minimize the morbidity. Samples were taken with CT-guided, stereotactic, small side-cutting Nashold biopsy forceps (diameter: 1 mm) [Figure 1C],[Figure 1D]. Histopathological diagnosis was based on intraoperative smear preparations and paraffin embedded sections. Postoperative CT scan was done routinely within two hours past surgery; any clinical deterioration within the first week after surgery was considered as morbidity. Patients who underwent biopsy in the awake stage were discharged on the same day unless their prebiopsy neurological condition was not good.
| Results | | |
Histological diagnosis was established in 23 patients [11 diffuse astrocytomas [Figure 3], eight pilocytic astrocytomas [Figure 4], two tuberculous lesions, one epidermoid cyst [Figure 5], and one infarction]. Although there was no procedure-related mortality, morbidity was minimal and temporary in three patients. No consistent correlation could be made between radiographic characteristics and histological diagnoses.
| Discussion | | |
Lesions of the brain stem constitute a separate group in neurosurgical paediatric pathology. [1],[6] Their histological diagnosis is essential for specific treatment. [2],[6] Different types of cysts can be found besides gliomas, tuberculomas, vascular malformations, radionecrotic lesions, or other masses. [3],[7] Open surgery is most appropriate in tumors of the cervicomedullary junction, dorsal exophytic tumors protruding into the fourth ventricle, cystic tumors, enhancing tumors with clear margins that exert a space-occupying effect, and finally, benign tumors ( i.e ., those with slow clinical progression). [2],[3] The approach of the different target locations by distinct routes, transcerebral and transcerebellar, is still a matter of debate. [7],[8],[9],[10] Moreover, pure medullary lesions are seldom biopsied, whereas diffuse brainstem lesions, typical of children's brainstem gliomas and rather frequent in most published series, depend less and less on the histopathological confirmation for treatment. [8],[9]
Our results indicate that biopsies of masses and fluid drainage of cystic lesions of the posterior fossa are safe and simple methods. Alternatively, open operative procedures to obtain tissue require a visible surface abnormality to guide the biopsy, and carry the risks of a major surgical procedure in already compromised patients. [3],[10],[11] For these reasons, the authors consider a suboccipital, transcerebellar, stereotaxic biopsy to be the diagnostic procedure of choice in the assessment of brain stem mass lesions. Advantages of biopsy are high positive biopsy rates (96%; Literature: 92-100%), differentiating benign lesions which could mimic glioma-like inflammatory granulomas, pyogenic abscess, epidermoid cyst; and in cystic lesions, rapid amelioration of neurological symptoms. [10],[11],[12] Keeping the patient awake and clinically monitoring during the procedure allows us to make the necessary changes in the trajectory of the biopsy probe to minimize the morbidity. Also, the awake transcerebellar biopsy can be done as an outpatient procedure which saves time and money.
Newer technology such as multi-planar, stereotactic magnetic resonance imaging and / or reformatted computed tomography imaging for coordinate determination and trajectory selection facilitates a completely intraaxial pathway through critical neural tissue. [1],[5],[11]
| Conclusions | | |
A stereotaxic approach to brain-stem lesions provides a high yield of positive histological diagnoses with a low incidence of morbidity. Awake CT-guided stereotactic biopsy via the suboccipital transcerebellar route in a semi-sitting position is a safe, reliable, and effective method for brainstem lesions, that can obtain adequate tissue for histological diagnosis, thus providing each patient with the best available treatment.
| References | | |
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| 2. | Nishio S, Takeshita I, Fujii K, Fukui M. Brain stem glioma: the role of a biopsy. Br J Neurosurg 1991;5:265-73. [PUBMED] |
| 3. | Selvapandian S, Rajshekhar V, Chandy MJ. Brainstem Glioma: comparative study of clinico-radiological presentation, pathology and outcome in children and adults. Acta Neurochir (Wein) 1999;141:721-6. |
| 4. | Frank F, Fabrizi AP, Frank-Ricci R, Gaist G, Sedan R, Peragut JC. Stereotactic biopsy and treatment of brain stem lesions: combined study of 33 cases. Acta Neurochir Suppl (Wien) 1988;42:177-81. |
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| 7. | Abernathey CD, Camacho A, Kelly PJ. Stereotaxic suboccipital transcerebellar biopsy of pontine mass lesions. J Neurosurg 1989;70:195-200. [PUBMED] |
| 8. | Pincus DW, Richter EO, Yachnis AT, Bennett J, Bhatti MT, Smith A. Brainstem stereotactic biopsy sampling in children. J Neurosurg 2006;104:108-14. [PUBMED] [FULLTEXT] |
| 9. | Coffey RJ, Lunsford LD. Stereotactic surgery for mass lesions of the midbrain and pons. Neurosurgery 1985;17:12-8. |
| 10. | Boviatsis EJ, Voumvourakis K, Goutas N, Kazdaglis K, Kittas C, Kelekis DA. Stereotactic Biopsy of Brain Stem Lesions. Minim Invasive Neurosurg 2001;44:226-9. |
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| 12. | Amundson EW, McGirt MJ, Olivi A. A contralateral, transfrontal, extraventricular approach to stereotactic brainstem biopsy procedures: Technical note. J Neurosurg 2005;102:565-70. |
[Figure 1A], [Figure 1B], [Figure 1C], [Figure 1D], [Figure 2A], [Figure 2B], [Figure 2C], [Figure 3], [Figure 4], [Figure 5]
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