CT-guided trigeminal tractotomy

:Acta

Acta Neurochir (Wien) (1989) 100:112-114

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N irochlrurgica 9 by Springer-Verlag 1989

CT-Guided Trigeminal Tractotomy Y. Kanpolat, H. Deda, S. Akyar, S. CaViar, and S. Bilgic Department of Neurosurgery, University of Ankara, lbni Sina Medical Center, Ankara, Turkey

Summary Trigeminal tractotomy is an effective procedure in denervating pain areas of 5th, 7th, 9th and 10th nerves. The classical imaging technique is the x-ray method which visualizes the target electrode relation indirectly. The method of CT-guided trigeminal tractotomy demonstrates the target electrode relation directly.

Keywords: CT-guidance; trigeminal tractotomy; target; direct visualization.

Introduction The collective topographic organization of the pain fibres of 5th, 7th, 9th and 10th nerves in the brain stem has made this region one of the important target points of ablative pain surgery. In 1937 Sj6qvist sectioned the descending tract of the 5th nerve at the level of the medulla oblongata by posterior fossa exploration 13. In later years the localization of the procedures was shifted to the caudal part of the medulla and upper spinal cord 15. In 1964 Kunc performed selective tractotomy 12mm above second cervical root level8. The first stereotactic trigeminal tractotomy was performed at the atlanto-occipital level by Hitchcock and then Crue et al. independent of each other z, 3. Hitchcock and Schvarcz used trigeminal tractotomy for the treatment of post-herpetic facial pain in 19724. In their paper they indicated that the accompanying trigeminal nucleus destruction might be responsible for the good results obtained in treating postherpetic neuralgia. Later Schvarcz approached the oral pole of the subnucleus caudalis at the level of occipito-cervical junction and named the procedure trigeminal nucleotomy 1~ Nucleus caudalis lesions are still performed with the help of multiple RF lesions for central trigeminal pain states by CI C2 laminectomy and a small occipital craniectomy 1' 12 Trigeminal tractotomy and/or nucleotomy are now

used for pain denervation in selected cases, especially for cancerogenic and deafferentative pains located in the areas of the 5th, 7th, 9th and 10th nerves ~' z, 3, 4, 7, 9, 11, 12, 14

In stereotactic trigeminal tractotomy, x-ray is the classical imaging method used for placing the electrode in the chosen target. Despite accompanying contrast agents, this visualization method can only indirectly specify the target electrode relationship. In this study, we are introducing a CT-guided procedure where the target electrode relation is visualized directly.

Material and Method CT-slices have been provided by Picker 1200 sx device. A three mm slice thickness has been used with 512 • 512 matrix; visualization quality has been improved by decreasing the diameter of the image provision. The patient is given 7 cc (240 mlg) of iohexol into the subarachnoid space by lumbar puncture. The patient is placed in the prone position on the CT-table with the head in the flexed position. Prior to application, it is checked whether the contrast substance is spread homogeneously obtaining slices from the upper spinal canal. In the meantime, the measurements of spinal cord diameters are taken. Following local anaesthesia, the subarachnoid space is reached at the occipito-cervical region with a No 20 Cordotomy needle, 5 7 mm lateral of the midline. The target is 3 mm anterior to the posterior aspect of the spinal cord and 6 mm from the midline at the first cervical segment (Fig. 1). The correct direction of the needle to the target is provided by means of CT-visualization (Fig. 2). Thus the 2ram open tip temperature monitoring Cordotomy electrode of Levin* is introduced towards the target. By obtaining new CT-slices, it is checked to see whether the electrode has penetrated the cord, how much the cord has been displaced, how much of the electrode has penetrated into the spinal cord, and whether the tip of the electrode is at the target point (Fig. 3). After the correct localization of the electrode has been checked by impedance measurement and stimulation, classical RF-lesions are made. This procedure has been used in two cases. In the first case, who was suffering from intractable * Radionics Inc. Burlington, Massachusetts, U.S.A.

Y. Kanpolat et

al.:

CT-Guided Trigeminal Tractotomy

Fig. l. Coordinates for the target point: 3 mm anterior to the posterior aspect of the cord and 6ram from the midline at the first cervical segment

! 13

Fig. 3. Final position of the electrode at the target point

and the electrode was placed in position. During the stimulation with 0.1 V of current she was very irritated and she described electrical or shock-like sensation on the left side of the face. She could not tolerate 55 ~ lesions for more than 20 seconds. Complete pain control was achieved following the procedure.

Discussion T r i g e m i n a l t r a c t o t o m y is an effective p r o c e d u r e in d e n e r v a t i n g n o t only the trigeminat p a i n areas but also the areas innervated by the 7th, 9th and 10th nerves. N o w a d a y s , trigeminal t r a c t o t o m y is p e r f o r m e d separately by open surgery 1' ~2 or p e r c u t a n e o u s stereotactic surgery2, 3, 4, 14. T h e a d v a n t a g e s o f the p e r c u t a n e o u s

Fig. 2. Correct direction of the needJe into the subarachnoid space at atlanto-occipital interspace

pain due to parotid carcinoma, the pain was dominantly located in the second and third division of the left trigeminal area and the oral cavity. After the application of electrode to the target (Fig. 3), the patient described shock-like sensation especially in the first and the second divisions of the trigeminal area with 0.2 V of the stimulation. With a 60sec lesions at 55 ~ complete pain control (analgesia) was achieved in the second and third divisions of the trigeminal area. The second case was suffering from hypoalgesic and neuralgic type of pain within the 5th and 9th nerve areas due to metastatic breast cancer. She was incapacitated and irritable due to attacks of pain. Carbamazepine was ineffective in controlling the pain attacks for the tast two weeks, In this patient, the target was approached

p r o c e d u r e are the following: its a p p l i c a b i l i t y u n d e r local anaesthesia in c o o p e r a t i o n with the patient, he being a w a r e o f the responses to the s t i m u l a t i o n ; its safe applicability even to patients whose general c o n d i t i o n is p o o r ; in case o f an u n s a t i s f a c t o r y result, the p r o c e d u r e can be r e p e a t e d easily. O n e o f the i m p o r t a n t questions in ablative stereotactic p a i n surgery on the b r a i n stem a n d u p p e r spinal c o r d is the visualization o f the target electrode relation. In the x - r a y imaging, target electrode relation c o u l d be visualized only indirectly despite the use o f w a t e r soluble c o n t r a s t agents. D i r e c t visualization o f target elect r o d e relation in stereotactic ablative p a i n surgery is possible only with C T - g u i d a n c e . T h e first a p p l i c a t i o n o f this k i n d was p e r f o r m e d by us in the extralemniscal m y e l o t o m y 6. T h e same i m a g i n g technique was a p p l i e d for p e r c u t a n e o u s c o r d o t o m y s a n d trigeminal tractotomy. I n t r i g e m i n a l t r a c t o t o m y a n d similar p r o c e d u r e s , the

114 most important problem is the correct insertion of the active electrode tip into the target point. In these types o f surgical procedures, most important guidance is obtained by impedance measurements. With this method it is possible to check whether the electrode system penetrates the tissue, but it is not possible to calibrate how much the tissue is penetrated. Therefore the establishment of the anatomical localization of the active electrode in the medulla and the upper spinal cord is determined by stimulation and recording of somatosensorial evoked potentials 2. In trigeminal tractotomy, the direct visualization of the target electrode relation can be made by means of CT-guidance. With this method, correct anatomical measurements can be obtained. By means of these correct measurements, it is possible to establish both the differences due to variation and the specifying of the target point as well as the exact target electrode relation on the direct image. Since the localization of the active electrode at the target is directly visible, we are convinced that it is possible to orientate the position more accurately with the movement of the active electrode in the antero-posterior direction. We are also of the opinion that localization can be provided easily with specially prepared curved electrodes. By means of changes in electrode technology we are able to reach any direction required. In the Levin electrode system, contrary to the R o s o m o f f needle electrode system, we have not observed puncture difficulties and displacement problems with the spinal cord. We believe that the easier penetration of the Levin electrode is due to its smaller calibre (0.27 ram). We believe that, from now on the new imaging technique of stereotactic ablative pain surgery in the medulla and the upper spinal cord should be CT. All procedures related to percutaneous cordotomy, extralemniscal myelotomy and trigeminal tractotomy have been performed under CT-guidance in our department since 1987.

Y. Kanpolat etal.: CT-Guided Trigeminal Tractotomy In conclusion, we can advocate that trigeminal tractotomy with CT-guidance provides direct visualization of the target electrode relation. This method is both safer and simpler than the classical methods.

References 1. Bernard EJ, Nashold BS, Caputi F etal(1987) Nucleus caudalis DREZ lesions for facial pain. Br J Neurosurg h 81-92 2. Crue BL, Carregal EJA, Felsoory A (1972) Percutaneous stereotactic radiofrequencytrigeminal tractotomy with neurophysiological recordings. Confin Neurol 34:389-397 3. Hitchcock ER (1970) Stereotactic trigeminal traetotomy. Ann Clin Res 2:131-135 4. Hitchcock ER, Schvarcz JR (1972) Stereotactic trigeminal tractotomy for post-herpetic facial pain. J Neurosurg 37:412417 5. Kanpolat Y, Deda H, Akyar S: CT-guided percutaneous cordotomy. Acta Neurochir (Wien) (in publication) 6. Kanpolat Y, Atala~ M, Deda H, Siva A (1988) CT-guided extralemniscal myelotomy. Acta Neurochir (Wien) 91:151-152 7. King RB (1985) Neurosurgery, vo13: Medullary tractotomy for pain relief. McGraw-Hill Book Company, New York, pp 2452-2454 8. Kunc Z (1965) Treatment of essential neuralgia of the 9th nerve by selectivetractotomy. J Neurosurg 23:494-500 9. Nashold BS, Crue BL (1982) Neurological surgery, vol 6: Stereotactic mesencephalotomy and trigeminal tractotomy. WB Saunders Company, New York, pp 3702-3716 10. Schvarcz JR (1975) Stereotactic trigeminal tractotomy. Confin Neurol 37:73-77 11. SchvarczJR(1977) Postherpeticcraniofacialdysaesthesiae:their management by stereotactic trigeminal nucleotomy. Acta Neurochir (Wien) 38:65-72 12. Siqueria JM (1985) A method for bulbospinal trigeminal nucleotomy in the treatment of facial deafferentation pain. Appl Neurophysiol 48:277-280 13. Sjoqvist OP (1938) Studies on pain conduction in the trigeminal nerve: a contribution to the surgical treatment of facial pain. Acta Psychiat Neurol [Suppl 17]: 1-139 14. Tood EM, Crue BL, Carregal EJA (1969) Posterior percutaneous tractotomy and cordotomy. Confin Neurol 31:106-115 15. White JC, Sweet WH (1969) Pain and the neurosurgeon. Ch C Thomas, Springfield, Illinois, USA, pp232-251 Correspondence and Reprints: Dr. Y. Kanpolat, Department of Neurosurgery, University of Ankara, ibni Sina Medical Center, Ankara, Turkey.