Original Papers 1989 S. Karger AG, Basel 0255-7975/89/0155-0217 $2.75/0 Pediatr Neurosci 1989;15:217-222 Stereotactic Resection of Pediatric Vascular Malformations' Michael D. Partington, Dudley H. Davis, Patrick J. Kelly Department of Neurological Surgery, Mayo Clinic and Mayo Graduate School, Rochester, Minn., USA Key Words. Arteriovenous malformation • Epilepsy • Intracranial hemorrhage ■Stereotactic technique Abstract. The technique of computer-assisted stereotactic resection of intra-axial neoplasms can also be used in the treatment of vascular malformations. We report a series of 12 pediatric patients with supratentorial lesions who underwent stereotactic resections between 1985 and 1988. There were 5 boys and 7 girls, with mean age 8 years (range 3-16). Epilepsy was the presenting symptom in 8 children, hemorrhage in 3, and in 1 the lesion was incidentally diag­ nosed. Seven lesions were angiographically occult. All lesions were resected without mortality or morbidity. Sei­ zures resolved in 7 of 8 cases, with the remaining patient experiencing a reduction in seizure frequency. Illustrative cases are presented. Vascular malformations in children occur infre­ quently but can be a cause of significant morbidity, par­ ticularly in the form of hemorrhagic stroke or epilepsy [1]. Therapeutic options most frequently discussed in the literature include conventional surgical approaches, interventional radiology and, most recently, stereotactic radiosurgery. In recent years, the safety and efficacy of volumetric, stereotactic resection of intra-axial brain neoplasms has been well established [2-4], In this report, we describe the use of this technique in the sur­ gery of pediatric vascular malformations. Illustrative cases are presented which demonstrate some of the unique applications of this technique, i.e. in localizing a small, superficial lesion, in approaching a deep lesion, in targeting the remnant of a previously operated mal­ formation and as an alternative to radiosurgery. 1 This paper was presented at the 18th Annual Winter Meeting of the Pediatric Section of the AANS, 1 December, 1989, Washington, D.C. Patients and Methods Clinical Data Twelve children (5 boys and 7 girls) underwent stereotactic resec­ tions at the Mayo Clinic between 1985 and 1988. Clinical features of these patients are summarized in table 1. The mean age at the time of surgery was 8 years (range 3-16). Eight patients had a history of sei­ zures and 3 presented after intracranial hemorrhages. In 1 case (pa­ tient 9), a child with a history of leukemia and previous prophylactic cranial radiotherapy, a lesion appeared on a screening CT which had previously been normal. Neurological examinations were normal in 5 patients. Of the 7 children with deficits, 4 had hemiparesis, 2 had changes in cognitive function and 1 had a third nerve palsy only. Preoperative imaging studies included a stereotactic CT and angio­ gram in all cases. In 7 patients the lesions were angiographically oc­ cult. Surgical Procedure The surgical technique used is similar to that previously described by Kelly et al. [2, 4), Kelly [3] and Davis et al. [5]. In each case, a CT/MRI-compatible stereotactic headframe was applied, usually under local anesthesia with intravenous sedation. The position of the headframe relative to the skull was measured using a set of detachable micrometers: this feature allows for accurate replacement of the headframe in those cases where surgery was not done on the same day as data acquisition. Each patient then underwent stereotactic angiog­ raphy and CT scanning and, in selected cases, MRI scanning. Ar­ chived data from the imaging studies was loaded into the operating Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 2/28/2020 7:44:49 AM Introduction 218 Partington/Davis/Kclly Table 1. Clinical features Patient Age years Sex Symptoms Examination Angiogram/CT 1 2 3 4 5 6 7 8 9 10 11 12 13 4 3 16 4 8 7 14 10 13 8 3 m m m f f CPS focal Sz. focal Sz. 1VH 1VH CPS single Sz. 1CH none ICH .CPS chronic Sz. chronic Sz., known TS hemiparesis normal normal normal 3rd nerve palsy inattentive normal hemiparesis, aphasia normal hemiparesis hemiparesis somnolent occult, Lt. parietal occult, Lt. frontal occult, Rt. frontal aVM, Rt. temporal AVM, Rt. caudate AVM, Lt. parietal occult, Lt. temporal AVM, Lt. parietal occult, Rt. frontal occult, Rt. frontal angioma, Lt. parietal occult, Rt. frontal r m m r f f f CPS =Complex partial seizures; Sz. = selzure; IVH = intraventricular hemorrhage; 1CH = intracerebral hemorrhage; TS = tuberous sclerosis. Patient Interval months Seizures ACDs Symptoms/exam 1 2 3 4 5 6 7 8 9 10 11 12 12 25 20 31 45 12 34 35 5 13 35 36 none none none NA NA none none NA NA none decreased none — none/normal none/normal none/normal none/normal none/normal none/normal none/normal unchanged none/normal none/normal none/normal none/normal + - - + - - + + + ACD = Anticonvulsant drugs; NA = not applicable. room computer system. Data was then digitized by the surgeon as fol­ lows: first, the localizing artifacts on the angiograms and on each CT/MR1 slice w'ere digitized. A target point was then selected in the center of the imaged lesion. This target point was then used as the center of a stereotactic volume created by outlining the boundaries of the lesion on each CT/MRI slice using acursor and trackball system. The stereotactic volume is created by an interpolation program which may be sliced orthogonal to any surgical approach angle selected by the surgeon. This enables the surgeon to ‘look ahead’ and view the outline of the lesion (on a video monitor) as it would appear from the surgical viewline. The computer then determined the threedimensional coordinates of the target point and calculated the X, Y and Z adjustments necessary to bring this point into the focal point of the arc-quadrant of the stereotactic frame attached to the operating table. The patient was then transferred to the operating table after general anesthesia was induced and a trephine craniotomy was car­ ried out through a linear scalp incision. Superficial lesions were dis­ sected out using suction and bipolar cautery technique. Deep lesions were approached using a cylindrical retractor (either 2 or 3 cm di­ ameter) which was mounted on the arc and advanced to the level of the lesion using laser dissection. The computer reconstructions of the lesion were then used to determine its borders and the lesions were then removed either by laser vaporization or by suction and bipolar technique. Results Overall results are summarized in table 2. Follow-up was obtained in all patients at a mean interval of 25 months (range 5-45). No new deficits were noted upon examination of the patients who were normal preoperatively. Of the remaining 7 patients, 6 had complete reso­ lution of their deficits and 1 patient (patient 8) was un­ changed. Follow-up of the 8 patients who presented with epilepsy was obtained at a mean interval of 23 months (range 12-36). Of these children, 7 (87.5%) were seizurefree, of whom 3 were off anticonvulsants. The other child (patient 11) experienced a reduced seizure frequen­ cy of less severe type. Illustrative Cases Patient 2. A 4-year-old male was evaluated because of an 11-month history of right facial focal motor seizures which were medically refractory. His interictal neuro- Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 2/28/2020 7:44:49 AM Table 2. Follow-up Stereotactic Resection of Pediatric Vascular Malformations 219 Fig. 1. Patient 2: Left posterior frontal AVM seen on MRI. Fig. 2. Patient 5: CT scan (a) and lateral view of a right carotid an­ giogram (b) showing an AVM in the head of the caudate nucleus. total resection of an AVM. Recurrent hemorrhage necessitated a second craniotomy in the acute postoper­ ative phase. At discharge, the patient had a mild left hemiparesis but was otherwise normal. She subsequent­ ly developed focal motor seizures involving the left face and arm which became medically refractory. At the time of her initial evaluation here at age 13 she was having an Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 2/28/2020 7:44:49 AM logical exam was normal. CT scanning revealed a nonenhancing, calcified left frontoparietal mass which on MR scanning had the appearance of a thrombosed vascular malformation (fig. 1). The lesion was avascular on angiographic studies. After stereotactic localization, the patient underwent a trephine craniotomy and resec­ tion of a 1-cm-diameter thrombosed arteriovenous mal­ formation (AVM). Postoperatively, the patient was un­ changed. At 25 months follow-up he remains neurologically normal and seizure-free on anticonvulsants. Patient 5. A 4-year-old female was taken to her local hospital after complaining of an acute headache and subsequently becoming unresponsive. At her initial evaluation she was somnolent but arousable to deep pain and had a right third nerve palsy but her exam was otherwise nonfocal. CT scanning revealed an intraven­ tricular hemorrhage. Cerebral angiography showed a small AVM in the head of the right caudate nucleus. She was transferred to this institution 1 week after her ictus. On arrival, her neurological exam was normal except for her cranial neuropathy. After obtaining a stereotactic CT and angiogram (fig. 2a, b), a 1-cm AVM was resected using a transfrontal approach with an entry point in the superior frontal sulcus. Postoperatively, the patient was unchanged and a follow-up angiogram was normal. At 45 months follow-up she remains neurologically normal. Patient 10. A 13-year-old female was evaluated be­ cause of intractable seizures after previous AVM sur­ gery. At 2 years of age she suffered a right frontal intraparenchymal hemorrhage and underwent cranioto­ my elsewhere for evacuation of the hematoma and sub- 220 Partington/Davis/Kelly Fig. 3. Patient 10: CT scan (a) and MR1 (b) with residual AVM in the bed of the previous resection. excess of one hundred seizures per month. Preoperative CT and MRI scanning revealed a contrast-enhancing deep right frontal parasagittal mass, which was angiographically avascular (fig. 3a, b). This lesion was tar­ geted and approached via the superior frontal sulcus. A complete resection was obtained (fig. 4). At 13 months follow-up her hemiparesis had resolved and she was sei­ zure-free on anticonvulsants. Patient 11. An 8-year-old female presented here with a 6-year history of intractable right focal seizures with secondary generalization. One and a half years prior to being seen at this institution a left parietal angioma was treated with a radiosurgicai device (gamma knife) and received a total dose of 5,000 cGy. Following this treat­ ment she initially had a decrease in seizure frequency over a 3-month period, but subsequently rebled and returned to her baseline level of seizure activity. On ex­ amination, she had mild weakness of the right arm of upper motor neuron type, with associated decreased coordination. After stereotactic imaging had been com­ pleted (fig. 5a, b), a venous angioma was resected without complications. At 35 months follow-up her arm strength and function was normal and she had a reduced frequency of focal seizures with no further generali­ zation. Repeat CT scanning showed no residual lesion (fig. 6). Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 2/28/2020 7:44:49 AM Fig. 4. Patient 10: Postoperative CT scan demonstrates no residual AVM. 221 Stereotactic Resection of Pediatric Vascular Malformations Fig. 6. Patient 11: Normal postoperative CT scan. Discussion Cerebral vascular malformations in children are un­ common. The overall population incidence in one large unselected autopsy series was 0.52% [6], with only 10-12% of diagnosed lesions occurring in the pediatric age group [7, 8]. The significance of these lesions lies in their role in the etiology of epilepsy and the sequelae as­ sociated with spontaneous hemorrhage [9], The overall risk of hemorrhage is 2.2%/year: each hemorrhage has a mortality rate of 29% and a risk of significant neuro­ logical morbidity of 25% [10]. The risk of bleeding has been shown to be higher in children than in adults and is also felt to increase with time [7]. For these reasons, obliteration of vascular malforma­ tions is favored over conservative management. Con­ ventional approaches can be used in the majority of cases with good results, but the challenge of small, su­ perficial or deep lesions is well recognized [1]. The stereotactic approach described above can readily be used in this situation and with demonstrated low mor­ bidity and mortality, as exemplified in cases 2 and 5. This also applies in the setting of residual malforma­ tions (see case 10). The recently developed modality of stereotactic radiosurgery has been widely employed in the management of these lesions [11], However, because of the risk of hemorrhage during the interval between treatment and the occurrence of thrombosis, a direct surgical attack may be preferred when feasible, as demonstrated in case 11. Our experience with these patients as well as adult pa­ tients with similar lesions has enabled us to determine which lesions are most amenable to this approach. The ideal lesion is less than 3 cm in diameter and is one which Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 2/28/2020 7:44:49 AM Fig. 5. Patient 11: Left parietal venous angioma shown on CT (a) and on lateral view of carotid angiogram (late arterial phase) (b). Partington/Davis/Kelly 222 would be difficult to localize using conventional tech­ niques. Lesions can be thrombosed or vascular, al­ though the space limitations imposed by the stereotactic retractor can place some constraints on the surgeon’s ability to apply vascular clips. Stereotactic craniotomies can be done in conjunction with electrocorticography and scalp electroencephalography, if the patient is un­ dergoing surgery for intractable epilepsy. It has been our experience that patients with medically intractable epilepsy associated with an intra-axial lesion will have significant improvement in their epilepsy after lesionectomy in the majority of cases [unpubl. data]. We have also confirmed this in the setting of occult vascular mal­ formations [12]. If the initial procedure does not result in significant improvement in seizure activity then the patient may be offered a formal lobectomy or other procedure where appropriate. In summary, computer-assisted stereotactic resection of vascular malformations is a safe and effective tech­ nique, with unique applications which make it an im­ portant addition to the surgical armamentarium. 4 Kelly PJ, Kail BA, Goerss SJ: Special stereotactic techniques: Stereotactic laser resection of deep-seated tumors; in Heilbrun MP (ed): Stereotactic Neurosurgery. Baltimore, Williams & Wilkins, 1988, pp 233-239. 5 Davis DH, Kelly PJ, Marsh WR, et al: Computer-assisted stereotactic biopsy of intracranial lesions in pediatric patients. Pediatr Neurosci 1988;14:31-36. 6 McCormick WF: Pathology of vascular malformations of the brain; in Wilson CB, Stein BM (eds): Intracranial Arteriovenous Malformations. Baltimore, Williams & Wilkins, 1984, pp 44-63. 7 Celli P, Ferrante L, Palma L, et al: Cerebral arteriovenous malfor­ mations in children. Surg Neurol 1984;22:43-49. 8 Martin NA, Edwards MSB: Supratentorial arteriovenous malfor­ mations; in Edwards MSB (ed): Cerebral Vascular Disease in Children and Adolescents. Baltimore, Williams & Wilkins, 1989, pp 283-308. 9 Kelly JJ Jr, Mellinger JF, Sundt TM Jr: Intracranial arteriovenous malformations in childhood. Ann Neurol 1978; 3:338-343. 10 Brown RD Jr, Wiebers DO, Forbes G, et al: The natural history of unruptured intracranial arteriovenous malformations. J Neu­ rosurg 1988;68:352-357. 11 Steiner L, Lindquist C, Steiner M: Radiosurgery with focused gamma-beam in children; in Edwards MSB (ed): Cerebral Vascu­ lar Disease in Children and Adoloescents. Baltimore, Williams & Wilkins, 1989, pp 367-388. 12 Davis DH, Kelly PJ: Stereotactic resection of occult vascular mal­ formations. J Neurosurg 1990;72:698-702. References Dudley H. Davis, MD Department of Neurological Surgery Mayo Clinic Rochester, MN 55905 (USA) Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 2/28/2020 7:44:49 AM 1 Humphreys RP: Arteriovenous malformations of the brain; in McLaurin RL, Venes JL, Schut L, Epstein F (eds): Pediatric Neu­ rosurgery. Philadelphia, Saunders, 1989, pp 508-516. 2 Kelly PJ, Kail BA, Goerss SJ, el al: Computer-assisted stereotaxic resection of intra-axial neoplasms. J Neurosurg 1986;64:427-439. 3 Kelly PJ; Volumetric stereotactic surgical resection of intraaxial brain mass lesions. Mayo Clin Proc 1988;63:1186-1198.