Definitive diagnosis of intracranial lesions is based on histopathological examination, culture and additional analysis of tissue obtained from the lesion. In case where surgical resection is not considered the optimal approach to treatment and diagnosis, minimally invasive biopsy techniques are considered the most appropriate way to obtain diagnostic data permitting a maximally informed approach to the therapy .
The purpose of this relation is to describe a mini invasive technique RMI guided to take a biopsy in a lesion located in the caudate nucleus. The patience is a Course dog , 9 years old , referred for seizures and depression.
MRI showed a circular solid 25 mm mass located in theright caudate nucleus area . The lesion appared to be isointhense T1, Hyperintense in T2, FLAIR, negative enhacement post contrast medium administration. The mass determined mass effect and perilesional edema.
FLAIR and T1 3D gradient echo sequences were performed after positioning on the head of the patience, through dental mod, fiducial markers that are able to create an hyperintense signal which can easily identified by the neuronavigation software.
FIG 1,2,3:Dorsal FLAIR, transverse T2 and T1 post contrast images at level of caudate nucleus area .The lesion appear to be iperintense on T2, FLAIR, isointense on T1 with negative enhacement.
The Brainsight modified system was used to get the biopsy. The biopsy was performed in surgical room.
Component of Brainsight stereotactic system:
FIG 4-5 : Component of brainsight stereotactic system
FIG 4: Surgical apparatus made with Cshaped surgical head clamp, tje articulated arm with digital ruler guide and needle in instrument sleeve, the subject tracker with three reflective spheres.
FIG5: standard computer with brainsight neuronavigation software , the surgical apparatus, the Polaris optical position sensor.
The dog, with the fiducial marker attached , was positioned in ventral recumbency, in the surgical head-clamp using four skull screws. The subject tracker, a system who works as reference coordinate system was attached to the head clamp. The Polaris optical position sensor was placed to visualize both the neuro-navigation pointer and the subject tracker. Following the steps outlined by the software every fiducial marker was registered. The centre of the fiducial marker (divot) correspond on the homologous marker seen in the RM images. In that way, moving the pointer to different positions on the skull surface we could seen in the computer screen the corresponding location as a 3D subject superimposed on 3D image reconstructions of the brain skull lesion and ventricle system. Moreover the pointer location is guided real time in 2D reconstruction of sagittal dorsal and oblique plains.
FIG 6-7: Images showing a 3D models with fiducial markers and and the trajectory planning.
For trajectory planning , the pointer was placed in the instrument sleeve of the articulated arm who has three separated joint that can be blocked in any position.
Once determinate the trajectory, the distance from the zeroing platform to the target , a 5 mm burr hole was made in the skull by an hand held drill. A 16 gauge needle was manually lowered, using the digital ruler guide, to the target and using a 5 mm syringe a sample was taken. The material was taken three different times at different deep level.
The dog did not presented any complication and was able to come back home in 24 hours . The cytological and histological examinations were suggestive of low grade diffuse astrocytoma
In the last years a variety of stereotactic approaches to brain biopsy have been described in dogs and cats involving both CT and MRI based system. Both the two methods allowed to catch samples from the tumor with low error margin and mini invasivity. Pelorus Mark 3 modified TC –guided system, for example, has reported to have valid biopsy in 98% of total cases . The Latnen modifie system in the 95% of cases. Brainsight modified system allowed to get intracranial biopsy using RMI images with the advantage to take biopsy in lesions less visible by CT studies because poorly margined, with negative contrast enhacement.
It allowed to get biopsy with high accurency in the histologic diagnosis of the lesion ( 100% in 6 studied cases ) and a low target error ( 1,79 mm ) . The surgeon is able to check the trajectory , to modify the target approach during the surgical procedure without having to reimage the patient position. The headclamp can be positioned in any position in the patient’s head to allow the best access to the desired target area Thanks to the dental mod, that permits position reproducibility , it is always possible to reach the target point in different times. Most of the Dogs who underwent the procedure could come back at their neurological original status in less of 12 hours after the end of the procedure
Chen AV et al: Clinical evaluation of a magnetic resonance imaging-guided, frameless stereotactic brain biopsy system in the dog ACVIM FORUM 2011.
Chen AV et al:Description and validation of a magnetic resonance imaging-guided stereotactic brain biopsy device in the dog. Vet. Radiol Ultrasound. 2012 Mar-Apr, 53 (2): 150-156
P.Moissonnier et al. : Stereotactic CT-guided brain biopsy in the dog. Journal of Small Animal Practice 2002 , March 43,115-123
Koblik PD et al. Modification and application of a Pelorus Mark III stereotactic system for CT-guided brain biopsy in 50 dogs.Vet Rad Ultrasound 1999;40:424-433
Czyz M et al. Intraoperative magnetic resonance –guided frameless stereotactic biopsies – initial clinical experience. Neurol Neurochir Pol. 2012 March-Apr, 46 (2): 157-160
Comments are closed.