Journal of Clinical Neuroscience (2002) 9(4), 391±399 & 2002 Published by Elsevier Science Ltd. DOI: 10.1054/jocn.2001.1008, available online at http://www.idealibrary.com on Clinical study The preservation and reconstruction of cerebral veins and sinuses Laligam N. Sekhar1 MD FACS, Amitabha Chanda2 MD MCH, Akio Morita3 MD 1 3 Mid-Atlantic Brain and Spine Institutes, Annandale, VA, USA, 2The George Washington University Medical Center, Washington, DC, USA, University of Tokyo, Tokyo, Japan Summary Although cerebral veins and venous sinuses are very important to the neurosurgeon, they have received adequate attention only recently. The consequences of cerebral venous occlusion are well known. When the venous outflow is compromised due to a lack of adequate collateral circulation, venous infarction follows, with swelling, haemorrhage and neuronal death. The clinical consequences will depend upon the region of involvement of the brain and the site of the infarcted tissue. The symptoms may include seizures, hemiplegia, aphasia, coma and death. Similarly, the consequences of cerebral venous sinus occlusion depend upon the availability of collateral circulation. When such collaterals are not available, papilledema and visual loss and a pseudotumour cerebri syndrome are observed in milder cases, whereas, severe diffuse brain swelling, coma and death may be observed in severe cases. Acute venous or venous sinus occlusion is potentially very dangerous, whereas slow and chronic venous or venous sinus occlusion is better tolerated. Even in such patients, some neurological manifestations may follow, when the collaterals are poor. & 2002 Published by Elsevier Science Ltd. CEREBRAL VEINS ± AVOIDANCE OF INJURY either side initially along the vein to allow its preservation (Fig. 2a & b). Subsequently, it is possible to dissect some of the veins away from the dura mater under the microscope. Many convexity veins turn forward and are densely attached to the dura near the sagittal sinus for a short distance, before they drain into the sinus (Fig. 3a). In such cases, the vein can be dissected away from the dura mater to allow its lengthening. In a similar fashion, the vein can be dissected away from the arachnoidal adhesions, and a small branch/tributary can be sacrificed, in order to allow its lengthening (Fig. 3b). With convexity parasagittal approaches, the brain retraction and the venous stretching must be kept to a minimum to Cerebral veins may be damaged during operations by three mechanisms: intentional coagulation and division to prevent their rupture, traction during an operation from their fixed drainage sites (into a dural sinus) causing their rupture, or damage during their dissection in the brain. Veins are more liable to be damaged than arteries, because they have thinner walls, and are not as tortuous as arteries, allowing them less ability to be manipulated before rupture. Additionally, both basal and convexity operations put them at stretch and at risk for rupture, whereas arteries are stretched mainly during basal operations. It is apparent that in order to avoid its rupture, a cerebral vein should be either stretched minimally by minimising the extent of brain retraction, or by releasing them from adhesions to allow their lengthening. With convexity operations, the dura mater must always be opened from lateral to medial direction, since a vein may drain into a dural venous lake in the paramedian area, or be densely adherent to the convexity dura. In such cases, a small strip of dura mater is cut on Fig. 1 Magnetic Resonance Venogram showing the different major intracranial veins. [SSS ˆ superior sagittal sinus; SS ˆ straight sinus; SV ˆ septal vein; ICV ˆ internal cerebral vein; GVG ˆ great vein of Galen; TS ˆ transverse sinus; S ˆ sigmoid sinus] VENOUS ANATOMY AND STRUCTURES AT RISK A detailed discussion of the venous anatomy (Fig. 1) can be found in other publications.1,5 Major cerebral veins are usually at risk during operations, which involve the displacement of the brain from the fixed drainage sites of the veins, e.g. transcallosal approach, subtemporal approach or the supracerebellar approach (Table 1). Similarly, venous sinuses are at risk whenever a pathological process directly involves them, or when they are divided in order to approach a deep-seated lesion. Received 21 March 2001 Accepted 8 May 2001 Correspondence to: Laligam N. Sekhar MD FACS, 3301 Woodburn Road, Suite 202, Annandale, VA 22003, USA. Tel.: ‡1-703-641-5911; Fax: ‡1-703-641-5944; E-mail: amitabha52@hotmail.com, lsekhar@aol.com Table 1 Approaches where the veins can be in jeopardy Interhemispheric approach Transcallosal approach Subtemporal approach Petrosal approaches Supracerebellar infratentorial approach 391 392 Sekhar et al. a a b b Fig. 2 (a) Dura has been opened leaving a small leaf attached to an adherent or early draining vein. (b) Further dissection of the vein has been performed, leaving some dura around the dural sinus. a c b d Fig. 3 (a) Illustrating how the convexity vein runs along the sinus before emptying into it. (b) demonstrating the dissection of the vein away from the sinus, allowing its stretching. prevent venous injury. In some cases when the target is at a depth (e.g. a deep-seated tumour or arteriovenous malformation), the approach trajectory may have to be changed away (Fig. 4a) from a major vein in order to prevent its damage. Other potential strategies include changing the approach side (e.g. right to left), or a small corticectomy (Fig. 4b, c & d). With basal lesions, veins at greatest risk for rupture are the temporal tip draining veins, and the vein(s) of LabbeÂ. In these instances, the better informed the surgeon before the operation about any aberrant venous anatomy, the better he or she could Journal of Clinical Neuroscience (2002) 9(4), 391±399 Fig. 4 (a) Shows modification of approach trajectory to minimise stretching of veins. (b) showing small corticectomy for the same purpose. (c) Showing ipsilateral approach. (d) Showing contralateral approach. avoid major problems. In the majority of patients, the temporal tip draining veins can be divided without problems. However, when the vein is large, or if the vein of Labbe is absent due to prior surgery or very small because of an anatomical variation, then it cannot be occluded. If there is a concern about whether a & 2002 Published by Elsevier Science Ltd. Cerebral veins and sinuses 393 vein can be safely divided, a temporary clip can be placed on it, and the brain observed for 5 to 10 minutes before its division. If facilities exist for the measurement of regional cerebral blood flow, then such measurement may show severe decrease. However, the authors have no experience with this technique. In some patients, the approach can be successfully changed from a subdural to an epidural approach to allow a large draining vein(s) to be preserved. The vein(s) of Labbe (Fig. 5a & b) are at risk for injury during subtemporal and transpetrosal approaches. In the majority of patients, moving the approach trajectory away from the venous drainage point makes it safer for the vein. The transpetrosal approach, the partial labyrinthectomy petrous apicectomy approach, the translabyrinthine approach, and the total petrosectomy approach, all move the surgeon away from the drainage point of the vein of LabbeÂ. However, in some patients, these strategies may not be enough to prevent excessive stretching of the vein. In some patients, the tentorium may be divided with minimal brain retraction and then the retractor can be placed on the tentorium rather than the a temporal lobe in order to prevent venous stretching. When the vein is very large and dominant with an anterior drainage site (Fig. 5b), then the approach may have to be changed to the retrosigmoid (or retrosigmoid ‡ orbitozygomatic with frontotemporal craniotomy) in order to prevent venous injury, especially on the dominant side. VENOUS RECONSTRUCTION Venous reconstruction is indicated in cases of accidental injury to large veins, if brain swelling is noted after the occlusion of a vein, or after the injury to any deep vein. In such patients, the easiest reconstruction may be by direct suture, using 8-0 nylon sutures (Table 2). If the anastomosis is under tension, some of the tension can be released by dural mobilisation. Even if the repaired vein is slightly stenotic, direct repair is usually successful. However, in many patients, a segment of the vein becomes missing, so that repair may be difficult without using a graft. In such patients, a segment of saphenous vein from the leg, or a vein from the forearm or the neck, or the radial artery may be used as an interposition graft.6 The use of a saphenous vein interposition graft to repair an injured large vein of Labbe is illustrated (case 1). The main problem with venous reconstruction is postoperative thrombosis. This occurs because of injury to the endothelium of the transplanted vein and the slow flow through the vein in general. We give the patients 2000 units of intravenous heparin during the reconstruction procedure, and keep the patients on aspirin subsequently. PRESERVATION OF CEREBRAL VENOUS SINUSES b Because they transmit a large volume of venous blood from the brain, the patency of the venous sinuses is very important to preserve the functional integrity of the brain. The outcome of venous sinus occlusion depends upon the presence of collateral channels (Table 3), and the acuity of occlusion (which is again related to the development of collaterals). Although it is commonly believed that the anterior third of the sagittal sinus can be occluded with impunity, in an occasional patient, such an occlusion may result in venous infarction in one or both frontal lobes. The only venous sinuses, which may safely be occluded in many patients (but not all), are: the cavernous sinuses, the superior petrosal sinuses, the non-dominant collateralised transverse and sigmoid sinuses. Occlusion of the cavernous sinus can be usually per- Table 2 Indications of reconstruction of cerebral veins Damage to large superficial or deep vein Brain swelling observed after venous occlusion Table 3 Fig. 5 (a) Normal type of vein of LabbeÂ. (b) Markedly anterior draining vein of LabbeÂ. & 2002 Published by Elsevier Science Ltd. Indication of reconstruction of cerebral venous sinuses Status of Collaterals Decision Excellent collaterals Reconstruction unnecessary Practice for surgeons Reconstruction recommended Occlusion dangerous Reconstruction only if unexpected injury Marginal collaterals Poor or no collateral Journal of Clinical Neuroscience (2002) 9(4), 391±399 394 Sekhar et al. a b Fig. 7 (a)&(b) Direct repair of sigmoid sinus after resection of schwannoma, which had encased the sinus. Fig. 6 Technique of inserting butterfly needle into the sinus following placement of temporary clip to occlude the sinus. formed without adverse effects on vision and the orbit due to the presence of many drainage channels from the orbit. In order to evaluate whether a venous sinus can be occluded safely, the preoperative angiogram must be carefully evaluated. In patients who have a partial sinus occlusion, it may be necessary to perform bilateral ICA injection to have a large contrast load, or to inject one carotid artery with manual compression of the contralateral carotid artery. Magnetic Resonance Venography (MRV) is useful to delineate the speed of flow through the sinus, but is inadequate to discriminate between slow flow and complete occlusion (Fig. 1). At surgery, before occluding a sinus, test occlusion must be performed (Fig. 6). In order to do this, the intrasinus pressure is measured by inserting a 20G butterfly needle connected to a pressure transducer. Normal venous sinus pressure should be less than 15 mm of Hg, depending upon the position of the head. After a stable reading has been obtained, a temporary clip is applied on the venous sinus at the appropriate period of expected occlusion. Observation of the brain or cerebellum for swelling, observation of the evoked potentials and of intrasinus pressure is performed, for at least five minutes. Intrasinus pressure is the most sensitive indicator of the three, but cerebellar swelling may occur very quickly. If brain swelling occurs, evoked potential change, or intrasinus pressure increases by more than 5 mm of Hg, then the temporary clip is removed and the idea of occluding the sinus is aborted. Even if the sinus is occluded, if the initial intrasinus pressure was above 15 mm of Hg, continuous monitoring of the pressure must be done during the rest of the operation, since a delayed increase in intrasinus pressure may occur and necessitate reconstruction. A balloon-occlusion test of the sinus was done in one patient. The patient was well for eight minutes, but then became acutely comatose because of severe brain and cerebellar swelling. After deflation of the balloon, resection of part of the cerebellum and a ventriculostomy, the patient made a very slow recovery to an independent state. Because of this experience, we consider balloon occlusion testing of the sinus to be dangerous. RECONSTRUCTION OF VENOUS SINUSES Direct Repair When a small portion of the circumference of a venous sinus is involved by a tumour such as meningioma, paraganglioma, or schwannoma, direct repair is recommended. In such patients, the tumour is excised, and the sinus is repaired with 5-0 prolene Journal of Clinical Neuroscience (2002) 9(4), 391±399 a b c Fig. 8 Repair of superior sagittal sinus by graft. (a) Tumour invading the sinus; (b) part of the patch graft is sutured to the sinus wall with tumour in situ; (c) Patch graft sutured after tumour excision. sutures either by direct suturing (Fig. 7a & b) or with a patch of dura mater or saphenous vein. In cases of sagittal sinus repair, the graft is sutured onto some of the sinus wall before removal of the tumour (Fig. 8a & b). After removal of the tumour, the sinus may be allowed to bleed if it is a small rent, occluded with finger pressure or temporary clips if some collaterals exist, or occluded with a balloon shunt if high flow exists through the sinus (Fig. 8c). If the repair is protracted, then the patient will need to be heparinized. When the sinus is divided to improve the exposure of a tumour or an aneurysm, direct repair may be performed with 60 prolene sutures (cases 3 & 4). Graft Reconstruction Graft reconstruction of the sinus is performed in cases of total segmental defect,7 which cannot be repaired directly as described above. The indications for such sinus repair are as discussed. In patients with excellent collaterals, such repair is redundant, and mainly provides practice for the surgeons. In patients with marginal collaterals, sinus resection and repair are recommended. In patients with poor or no collaterals, the sinus should be left open with residual tumour. In such cases repair is only indicated in cases of accidental injury. The saphenous vein, extracted from the thigh, is used (Fig. 9a & b) when the sinus to be repaired is large (1cm or more in diameter). When the sinus has been previously removed by the tumour, the radial artery may be prepared because it tends to stay open even when the flow rate is low. The artery should be distended under pressure with heparinized saline in order to relax vasospasm. Because of the discrepancy in size, an end-toside technique is used for radial artery grafts (Fig. 10a & b), whereas an end-to-end technique is used for saphenous vein grafts (cases 1 & 2). & 2002 Published by Elsevier Science Ltd. Cerebral veins and sinuses 395 a b Table 4 Results of venous reconstruction from 1993 to 1999 Type of vein/venous sinus reconstructed No of patients No of patients in which they are patent finally 1 1 1 1 1 1 2 2 5 1 NA 1 4 2 2 2 1 2 Cortical vein Resuture Graft SVG RAG Superior sagittal sinus SVG Transverse sinus (Pineal region) Division only Division ‡ SVG Fig. 9 (a) Tumour encased and invaded the sigmoid sinus to narrow the sinus. (b) Part of the sinus was resected along with the tumour and an interposition graft (Saphenous vein) placed (end-to-end anastomosis). Sigmoid sinus-jugular vein Division ‡ resuture Repair after tumour excision SVG SVG ˆ Saphenous Vein Graft; RAG ˆ Radial Artery Graft a b a b Fig. 11 Axial (a) and sagittal (b) contrast enhanced T1 image of MRI scan showing petroclival meningioma in case 1. a b Fig. 10 (a) Tumour invading sinus. (b) Tumour resected with sinus and interposition graft (radial artery) placed (end-to-side anastomosis). Results of vein and sinus reconstruction in the last six years are shown in Table 4. Fig. 12 (a & b) Venous phase of angiogram showing prominent vein of Labbe and dominance of the right lateral sinus. CASE ILLUSTRATIONS Case 1: A 58 year old female patient, known to have diabetes mellitus, hypertension and mitral stenosis, presented with facial pain and numbness. MRI showed a right petroclival meningioma (TED ˆ 2.17 cm) extending into the Meckel's cave and the cavernous sinus. There was mild brainstem compression (Fig. 11). Venous phase of angiogram showed a prominent vein of Labbe (Fig. 12). Surgery was done in September 1997. A transpetrosal retrolabyrinthine approach was used. Gross total excision of the tumour was done. However, during surgery, an aberrant vein of LabbeÂ, draining the entire temporal lobe and draining into a dural sinus anterior to the transverse sinus, was damaged. Because significant temporal lobe swelling was noted, the vein of Labbe was reconstructed with a short saphenous vein graft & 2002 Published by Elsevier Science Ltd. Fig. 13 Diagrammatic representation of the vein graft technique. Fish mouth opening is made in the vein as well as in the graft to reduce the amount of stenosis later on. Also a part of the sinus wall was removed. Journal of Clinical Neuroscience (2002) 9(4), 391±399 396 Sekhar et al. a b Fig. 17 Contrast enhanced axial (a) and sagittal (b) T1 image of MRI of case 2 showing a glomus jugulare tumour. Fig. 14 Diagrammatic representation of the vein graft technique (Contd). The anastomosis completed and a pad of fat supports the graft. a b Fig. 18 Angiogram of patient (case 2) showing good cross circulation (a) and patent torcular Herophili and dominant right lateral sinus (b). Fig. 15 Operative picture of the completed anastomosis. The arrow points to the saphenous vein graft. Fig. 16 Three-dimensional CT-angiogram of case 1 showing patent graft and sinus. Journal of Clinical Neuroscience (2002) 9(4), 391±399 from the vein to the sigmoid sinus (Fig. 13). A special technique of venous attachment to the sigmoid sinus was used without significant flow interruption, by placing the attaching sutures first, and then cutting the hole into the sinus before tying the sutures (Figs 14 & 15). Tumour was seen to involve the trigeminal fascicles severely. The temporal lobe swelling resolved postoperatively and the patient recovered well. Postoperatively, the patient had partial sixth cranial nerve palsy and diminished sensation in V1 and V2 region and absent corneal reflex. Postoperative MRV and three-dimensional CT angiogram showed patency of the graft (Fig. 16). After two year follow up there was no tumour recurrence. The sixth cranial nerve palsy has disappeared totally, but trigeminal loss persisted. The venous reconstruction was felt to be important in this patient in avoiding major problems. Case 2: A 62 year old male presented with history of recurrent seizure with prickly tongue, distorted speech, numbness in 1976, 1983 and 1995. During an airplane flight he had severe dizziness and loss of hearing, which resolved spontaneously. He also had pulsatile tinnitus. On examination he had 20% hearing loss in his right ear and was unable to perform tandem walk. He had nystagmus. MRI scan showed a highly vascular glomus jugulare tumour (TED ˆ 2.42 cm) in the jugular foramen (JF) filling the region of right jugular bulb (Fig. 17) without occluding the sigmoid sinus (SS) and internal jugular vein (IJV) (Fig. 18). The tumour encased the petrosal segment of the internal carotid artery (ICA) bowing it forward. The cerebral angiography showed, that the tumour was supplied by an enlarged right ascending pharyngeal artery with additional supply arising from meningodural branch of right occipital artery, small branch of right posterior auricular artery and meningohypophyseal trunk. Surgery was done in November 1995. The sigmoid and transverse sinuses were larger on the right side but were subtotally occluded by the tumour. There was a good communication between the two sinuses at the torcular Herophili (Fig. 18). & 2002 Published by Elsevier Science Ltd. Cerebral veins and sinuses 397 a b Fig. 19 (a) Diagrammatic representation of the vein graft done to reconstruct sigmoid sinus. (b) Operative picture showing the vein graft (black arrow). Fig. 22 (a & b) Operative picture of case 3 showing temporary clips are placed on the lateral sinus (arrow showing the segment of the sinus in between the clips) and then cut in between the clips. Fig. 20 Postoperative angiogram showing patent graft (arrows) in case 2. Fig. 21 Angiogram of case 3 showing aneurysm at the vertebrobasilar junction. Therefore it was felt to be safe to occlude the sinus during tumour resection. At operation, the intrasinus pressure was measured prior to sinus occlusion and excision of the tumour (Fig. 6). Although the intrasinus pressure was initially unchanged after occlusion, the pressure increased steadily during the operation in the range of 35 to 40 torr. Because of this, reconstruction of the sinus was elected and was performed with a saphenous vein graft (Fig. 19). A 5 cm long vein graft was sutured from the sigmoid sinus to the internal jugular vein. Patency of the graft was verified by intraarterial and magnetic resonance angiography (Fig. 20). Postoperatively the patient had communicating hydrocephalus for which lumboperitoneal shunt was done. The patient had transient postoperative facial nerve palsy, which recovered completely. After a follow up of 21 months, the patient was seen to have & 2002 Published by Elsevier Science Ltd. Fig. 23 Intraoperative picture of case 3 showing the aneurysm. very mild impairment of tandem gait. There was no recurrence of the tumour and there was no other neurological deficit. Case 3: This 40 year old man presented at another institution with subarachnoid haemorrhage. He rebled and deteriorated. He was Hunt and Hess grade IV at admission and with a Fisher grade 4 hemorrhage. Cerebral angiogram revealed aneurysms at vertebrobasilar junction (VBJ) and at middle cerebral artery (MCA) bifurcation (Fig. 21). As the aneurysm at the vertebrobasilar junction has bled, it was operated upon first in May 1997. A retrosigmoid and transmastoid presigmoid approach was performed for exposure. In order to enhance the exposure we planned to transect the sigmoid sinus (Fig. 22). The left sigmoid sinus was slightly larger than Journal of Clinical Neuroscience (2002) 9(4), 391±399 398 Sekhar et al. a Fig. 24 Postoperative angiogram of case 3 showing patent sinus. b Fig. 26 Preoperative angiogram of case 4. (a) Tumour blush, although no major supplies from PCA. (b) Venous phase showing good collateralisation of the two lateral sinuses and the dominance of the right sinus. Fig. 25 Preoperative sagittal, coronal and axial enhanced T1 MRI scans of case 4 showing a pineal region tumour compressing the brainstem producing hydrocephalus. the right sigmoid sinus. Intrasinus pressure was measured to be 12±13 mm of Hg before occlusion. With occlusion, sinus pressure went to 18 mm of Hg. During surgery the sinus pressure went once to 20 mm of Hg. Both vertebral arteries were occluded temporarily for 31 minutes and mild hypotension was also used. The Somatosensory Evoked Potential (SSEP) deteriorated initially and then improved after raising blood pressure to normal and when temporary clip was removed from the vertebral artery. The aneurysm neck was at the vertebrobasilar (Fig. 23) fenestration and the aneurysm was occluded with two long clips. A minor intraoperative rupture was managed uneventfully. The sigmoid sinus was resutured directly with 5-0 and 6-0 prolene. Intraoperative angiogram showed patency of the sinus (Fig. 24). The patient had a stormy postoperative period with meningitis Journal of Clinical Neuroscience (2002) 9(4), 391±399 Fig. 27 Postoperative enhanced axial T1 image of MRI scan showing complete tumour removal of case 4. & 2002 Published by Elsevier Science Ltd. Cerebral veins and sinuses 399 Fig. 28 Preoperative enhanced MRI scan of case 6 showing colloid cyst of third ventricle. Fig. 29 Postoperative CT scan of case 6, showing venous infarct. and pneumonia. He also had postoperative vasospasm and underwent angioplasty. However, he recovered well and subsequently underwent elective clipping of the unruptured MCA aneurysm. At follow up six months postoperatively, he was found to be neurologically intact and has returned to his work. Case 4: A 46 year old man presented with a history of mental deterioration and gait ataxia. MRI scan showed a giant pineal region meningioma (TED ˆ 4.08 cm) compressing the brainstem severely and producing hydrocephalus (Fig. 25). An arteriogram (Fig. 26) in the venous phase showed good collateralisation of the two transverse sinuses and the non-dominance of the left side. The lesion was initially approached by a supracerebellar infratentorial approach, with the patient in a sitting position, but this was difficult and found to be inadequate for tumour resection. The patient was reoperated on by a combined approach (occipital, transtentorial, supracerebellar, transsinus approach) in a semiprone position. The transverse sinus was clipped and the pressure was measured. The intrasinus pressure before clipping was 8 mm of Hg and after clipping was 9 mm of Hg. The sinus was transected between two temporary clips. The tumour was debulked and the capsule of the tumour was dissected away from the brainstem and the encased veins. The transverse sinus was resutured with 5-0 prolene. The postoperative recovery was good and after a follow up of 61 months the patient had no neurological deficits and there was no recurrence of the tumour (Fig. 27). (Note: In this patient, as in case 3, the reconstruction of the sinus was mainly to preserve both sinuses for the future, and was not mandatory). Case 5: A 55 year old woman presented with loss of smell and taste for three months. She had been operated previously for & 2002 Published by Elsevier Science Ltd. bifrontal parasagittal meningioma before. MRI Scan revealed a recurrent tumour with TED of 3.00 cm. Surgery was done in October 1998. Although the superior sagittal sinus was thought to be occluded on angiography, it was found to be partially open during surgery. At operation, the sinus was opened, intrasinus tumour was removed totally and the sinus was repaired directly with 6-0 prolene. The patient had an uneventful recovery and after a follow up of 18 months she has no recurrence or new neurological problems. Case 6: A 47 year old man presented with headache, popping sensation in the head and some memory problems. Magnetic resonance imaging showed a colloid cyst of the third ventricle (Fig. 28). Preoperative angiogram was done to see any major draining vein to the superior sagittal sinus. He was operated on in February 2000. Transcallosal approach was done and complete excision of the tumour was done. There was no venous injury during the surgery. The patient did well in the immediate postoperative period, but later on had seizure and became somnolent. Computed tomographic scan showed haemorrhagic infarct in the right frontal lobe (Fig. 29). He was managed with diuretics and steroids. He gradually recovered alertness. He was found to have hypercoagulable state (Factor II mutation Prothrombin 20210 G"A, heparin induced antiplatelet antibodies). He was discharged from the hospital with left hemiparesis. However, the hemiparesis gradually resolved completely over three weeks. He was subsequently put on anticoagulation and is leading an active life at 6 month follow up. CONCLUSION Cerebral veins and venous sinuses are of great importance to the neurosurgeon to ensure optimal postoperative outcome for the patient. The importance of veins and venous sinuses are gradually being appreciated and understood. The so-called innocuous veins of yesteryear are now being shown as not so innocuous. Further research in this area is necessary. REFERENCES 1. 2. 3. 4. 5. 6. 7. Krayenbuhl H, Yasargil MG. Radiological anatomy and topography of the cerebral veins, in Vinken PJ, Bruyn GW (Eds.), Handbook of Clinical Neurology. Vascular Diseases of the Nervous System, part 1, Vol. II. Amsterdam: North-Holland, 1972, 102±117. Matsushima T, Rhoton AL Jr, De Oliveira E, Peace D. Microsurgical anatomy of the veins of posterior fossa. J Neurosurg 1983; 59(1): 63±105. Oka K, Rhoton AL Jr, Barry M, Rodriguez R. Microsurgical anatomy of the superficial veins of the cerebrum. Neurosurgery 1985; 17(5): 711±748. Schmidek HH, Auer LM, Kapp JP. The cerebral venous system. Neurosurgery 1985; 17(4): 663±678. Sakata K, Al-Mefty O, Yamamoto I. Venous consideration in petrosal approach: Microsurgical anatomy of the temporal bridging vein. Neurosurgery 2000; 47(1): 153±161. Morita A, Sekhar LN. Reconstruction of the vein of Labbe by using a short saphenous vein bypass graft. Technical note. J Neurosurg 1998; 89(4): 671±675. Sekhar LN, Tzortzidis FN, Bejjani GK, Schessel DA. Saphenous vein graft bypass of the sigmoid sinus and jugular bulb during the removal of glomus jugulare tumours. Report of two cases. J Neurosurg 1997; 86(6): 1036±1041. Journal of Clinical Neuroscience (2002) 9(4), 391±399