Abstract
Cavernomas may arise everywhere in the Central Nervous System. These benign vascular lesions can be really harmful for the patient provoking death or severe neurological disability. Surgery is the most effective treatment for the cure of the patient, but complications due to the procedure may appear. The avoidance of untoward postoperative morbidity includes the prediction of the behavior of the lesions in terms of trend to bleed, the appropriate selection of the surgical candidate and a careful planning of the surgical procedure. In spite of this exquisite and thorough evaluation and management, complications may appear. This chapter deals with the potential morbidity related to cavernoma surgery and its avoidance.
Keywords
cavernoma surgery, complications, avoidance of complications
Highlights
- •
The most frequent complication in cavernoma surgery is the damage of the surrounding central nervous tissue during resection and/or during the approach to the lesion.
- •
Cavernomas are benign lesions that frequently have a favorable course. The first step in prevention of postoperative complications is the appropriate selection of the surgical candidate.
- •
To avoid complications in cavernoma surgery, the selection of the entry point in eloquent areas and meticulous technique are of paramount importance.
Background
Cavernomas are vascular cavernomatous (cavernous angiomas) lesions histologically characterized by abnormal vessels with large capillaries. There is little or no cerebral brain tissue in the lesion. The natural course of cavernous malformations is rather unpredictable. The malformations may arise in and outside the central nervous system. Cerebrum, cerebellum, brainstem, and spinal cord are common sites of origin. Multiplicity of lesions is not rare (“cavernomatosis”), and there is also great disparity in size and locations. “De novo” lesions are seen in some instances as well as familial cases. Bleeding is the most devastating presentation, sometimes leading to death in the first episode.
Cavernomatous lesions can lead to bleeding in a variable fashion irrespective of the location. Symptoms and clinical deficit will be in accordance to the severity of the hemorrhage and neurologic territory. Supratentorial cavernomas may provoke seizures. The risk of hemorrhage (rehemorrhage) and the presence of seizures are the most frequent reasons to undertake surgical removal. The risk for hemorrhage is estimated between 0.6% and 5% (annual rate). Among those who bleed, 30% will rebleed over time. There is some assumption according to which once the cavernoma bleeds, the risk of rebleeding will persist for life. This is considered the major indication for surgery because the severity of the clinical deficit would increase over time due to further episodes of hemorrhage. Another reason for surgery is epilepsy in certain contexts. Also de novo cavernomas or growing lesions should be removed. Radiosurgery has also been advocated as a treatment modality for cavernoma, not without debate. Large metaanalysis studies conclude that long-term effects for stereotactic radiosurgery are unknown.
Brainstem cavernomas can produce a great variety of symptoms and neurologic deficit according to the location. Long tract involvement and cranial nerve dysfunction are very frequent. At the spinal cord, cavernomas have the same consideration as mentioned earlier, with the exception of seizures. Symptoms and neurologic deficit are related to spinal cord dysfunction. Lesions at the superficial pial layer can be removed without major postoperative consequences. Small lesions anteriorly placed are the most problematic for excision.
Cavernomas are associated with venous anomalies, sometimes very prominent. Venous anomaly is the current denomination, after having been very frequently reported as venous angiomas for many years. Unlike some other vascular malformations at the central nervous system, far from being removed or coagulated during surgery, these structures must be preserved to maintain normal venous drainage and to avoid venous infarction. Some authors do consider the coexistence of a cavernoma and a venous anomaly a risk factor for rebleeding.
The Choice of the Surgical Candidate for Cavernoma Removal
It has been extensively assumed that surgery is the best option to treat symptomatic cavernomas, even in difficult areas like the brainstem. This opinion is not unanimously accepted, showing that the decision is usually controversial and varies according to surgeons, institutions, and published articles. The decision must be made on a case-to-case basis that balances the risks of surgery and the experience of the surgical team against the natural history of the disease.
Bleeding is one of the indications for surgery. The recommendation for surgery is influenced by the estimated risk of future bleeding (that is, the natural history of the lesion), the neurologic injury predicted to occur with such a hemorrhage, and the patient’s clinical situation with special attention to neurologic condition, age, and the size and location of the lesion. Intralesional bleeding is a very common finding and doesn’t itself represent an indication for surgery. Acute extralesional hemorrhage is considered a clear sign of the potential aggressiveness of the lesion. Mass effect due to hemorrhage is a formal indication for removal of the clot along with cavernoma excision, which sometimes must be done in emergency basis. The decision also must be individualized after assessing a combination of different factors. One of them is the timing of the first episode of bleeding, and another is the age of the patient. Surgical removal should not be encouraged for older patients with very late bleeding. Early bleeding and younger patients would lead toward a more aggressive attitude because outcome is linked to the rate of further episodes of rebleeding.
Another important parameter is the location of the cavernoma. Cavernomas in “eloquent” areas are poorer candidates. Some series have published rates as high as 47% impairment after surgery in such “eloquent” areas (optic pathways, brainstem, motor and speech area). This anatomic fact must be combined with the cavernoma’s size and its deep or superficial location. Small cavernomas can be a problem regarding intraoperative identification and also postoperative morbidity. Bigger and superficial lesions would have less chance for neurologic morbidity.
Another important consideration for surgery is epilepsy. The lack of control of epilepsy in spite of medical treatment, a situation that is not infrequent when the lesion is harbored at the temporal lobe, is a formal indication. Another reason to advise the surgical excision of cavernoma is the attempt to “cure” epilepsy, removing the cause in the context of surgery of focal epilepsy. This would allow for discontinuation of the antiepileptic drug, which is of paramount importance when the patient is very young. Microsurgical resection of cavernomas responsible for intractable epilepsy is very much linked to the debate about the extent of tissue surrounding the cavernoma that needs to be removed to achieve the best outcome for epilepsy, which in some series is as high as 87% seizure-free.
A third indication for surgery on cavernomas is the progressive growth of the lesion (after preexisting lesion or “the de novo appearance”) and/or recurrence.
General Principles of Cavernoma Surgery to Avoid Morbidity
Once the decision has been made to perform cavernoma surgery, several principles and rules must be considered. Regarding the surgical approach, supratentorial or cerebellar lesions usually need standard craniotomies centered in the malformation. Brainstem cavernomas may require sophisticated skull base techniques to get access to the malformation. Lesions at the cerebrum and cerebellum may require entrance through the sulcus and/or linear incisions. The brainstem requires entrance through the already recognized “safe entry points” and/or an elongated puncture point. As a general rule, the direction of the entrance is given establishing a line connecting the center of the lesions with the point where the cavernoma is abutting with the pial surface (“two points”). A small window to the cavernous malformation is created, with the direction of access defined by the safest anatomic corridor possible.
The essence of the avoidance of neurologic morbidity (the most worrisome complication) is the preservation of the white and gray matter surrounding the cavernomatous malformation. The configuration of the cavernoma includes a more or less definable cleavage plane (gliosis and/or hemosiderin) that is the real clue for neurologic preservation. Bulky lesions need previous intralesional removal to achieve a very good preservation of this plane. Racemose and very irregular tumors can make the preservation of the surrounding tissue difficult.
As an ancillary intraoperative procedure, neurophysiologic neuromonitoring is nowadays crucial for the resection of these lesions in eloquent areas. The standard neurophysiologic techniques (cortical and subcortical mapping, cranial nerves, motor evoked potentials (PEM), somatosensory evoked potentials (SSEP)) are complemented by fourth ventricle mapping when the removal requires the penetration of such an eloquent anatomy at the brainstem.
Complications Related to Operative Technique (and Their Avoidance)
The Lesion Doesn’t Appear
This frustrating intraoperative complication was more common before the era of the intraoperative image. Deep cavernomas need intraoperative imaged-guided resection, among them neuronavigation. This technique can help anywhere in the central nervous system. At the brainstem it can help find the most suitable point for entrance. Ultrasonography can be also used in the cerebrum, cerebellum, and spinal cord. Smaller lesions are, of course, more problematic. Even with an intraoperative image, the lesion can be missed because the displacement of the white matter during the subcortical penetration can displace the cavernoma in its vicinity.
Neurologic Deficit After a Wrong Approach and/or Wrong Entry Point
These neurologic complications may arise when the direction of the approach given by the craniotomy/osteotomy (the surgical approach, in a general sense) is not appropriate and implies excessive retraction and/or distortion of the cortical or subcortical brain, brainstem, or spinal cord. The standard supratentorial or suboccipital craniotomies give a very straightforward route to lesions of the cerebrum and cerebellum. Sulcal navigation offers the best chance for gray and white matter preservation. The vicinity of the motor cortex, speech areas, and pyramidal tracts deserves special interest and the application of the current intraoperative refinements and armamentarium.
Brainstem lesions represent by far the most challenging operations. Brainstem cavernous malformations are associated with higher hemorrhagic rates and poorer neurologic outcome. Immediate postoperative impairment can be 35% to 45%, and long-term morbidity is no less than 15% in a metaanalysis of 1390 patients. The concept of a “safe entry zone” is crucial at the brainstem.
Cavernomas at the posterior medullary region can be entered through the median, paramedian, and lateral sulcus (similar to intramedullary tumors). When the cavernoma is anteriorly placed at the medulla, a far lateral approach must be taken to get the antero-lateral safe entry point at the medulla: the retro-olivary sulcus, particularly between the exit of the XII nerve and first cervical root. This approach allows maneuvering in front of the lower cranial nerves. Transclival endoscopic approaches would expose anteriorly the intradural foramen magnum area. The dorsal pontine region does allow the fourth ventricle to be entered through the median sulcus. Another entry point is the so-called pericollicular area (supra- and infrafacial triangles). The latter route avoids the nuclei and paths of the VI and VII nerves. The ventral/ventrolateral pontine brainstem can be approached through several surgical strategies: the simple retrosigmoid approach, the transpetrous approach, and the presigmoid approach. There are two main safe entry zones: One of them is the peritrigeminal area, right in front of the exit of the V nerve. This entrance is just lateral to the corticospinal tract. The other safe entry zone is the exit between the V and VII cranial nerves, which is very accessible through a retrosigmoid craniotomy. The supratonsillar approach has been described to reach the inferior cerebellar peduncle. The ventral mesencephalon can be approached through a frontotemporal craniotomy with the addition of a zygomatic osteotomy. Because cerebral peduncles do contain the corticospinal tracts in a very tight fashion (unlike the anterior pontine region, in which the corticospinal tract is found to be very loose), morbidity after surgery at this level can be very high. The subtemporal approach can also be useful for certain intrinsic anterior or lateral mesencephalic lesions. The subthalamic lateral mesencephalon can be approached looking for the safe entry zone called the lateral mesencephalic sulcus, bounded by the lateral mesencephalic vein. This entrance needs a suboccipital craniotomy with the addition of a supratentorial osteotomy allowing for upper retraction of the transverse sinus and (sometimes) cutting and opening of the tentorium according to its shape and conformation (paramedial suboccipital supratentorial approach). Thus the lateral mesencephalic sulcus can be approached. The opening of the lateral mesencephalic sulcus leads to the junction of corticospinal and lemniscal tracts. The dorsal mesencephalon/tectal plate can be reached through a supracerebellar-infratentorial approach, a suboccipital-transtentorial approach, or a combination of both. The collicular plate can be penetrated through the infracollicular safe entry zone. In spite of the presumed high morbidity when dealing with brainstem structures, a very acceptable postoperative morbidity has been published.
At the spinal cord, strict intramedullary cavernomas must be approached in a fashion similar to that of any other kind of tumor inside the spinal cord. When the tumor abuts the surface, the lesion itself provides the access. In spite of that, a superficial cavernoma at the spinal cord does not seem to show a better outcome than deeper lesions. One important consideration must be made in regard to pure anteriorly placed cavernomas. For these cases, a ventral approach to the spinal cord through a vertebrectomy has been sometimes indicated. Anterior cavernomas have the added problem of the vicinity of the spinal anterior artery.
Intraoperative Bleeding
Cavernous angiomas have been classically defined as occult malformations at angiography. In spite of this, not infrequently one of several arterial feeders of variable diameter can be identified during surgery. This can be the explanation for why some of them tend to rebleed, occasionally in a profuse manner ( Fig. 13.1 ). Intraoperative rupture and bleeding can be a big problem in areas like the brainstem or in deep-brain areas like the thalamus, leading to increased postoperative morbidity. The intraoperative identification of feeders in such a crucial anatomic region is not easy. Preoperative angiography can help in some cases, providing useful information if high vascularity is suspected. Normal venous anatomy and any suspected venous anomaly must be preserved during the procedure.
Timing for Surgery
Timing for cavernoma surgery is a very important aspect of the management of these malformations. Emergency-based surgery must be done only in case of neurologic deterioration, which fortunately happens only in a very restricted percentage of cases. This ultra-early surgery carries, of course, obvious risk and also the possibility of having remaining fragments in the hemorrhagic bed that later on can rebleed. Surgical timing appeared to influence the treatment results. Mathiesen et al. compared patients who underwent surgery within 1 month after the latest hemorrhage with those who underwent surgery at a later time. Transient neurologic deterioration was detectable in 15 of 17 patients who were treated later and in only 4 of 12 patients who were treated early. Bruneau et al. published their series of patients with “early” surgery after a first episode of bleeding at the brainstem with rather good results (improvement of more than 90%), thus avoiding the postoperative morbidity of the “delayed” surgery and preventing further bleeding. In spinal cord surgery for cavernoma, surgery within the first 3 months is also followed by a better outcome. Several publications have shown late surgery to be significantly associated with worse outcomes, but timing for surgery has also to be considered under the difficulty of every case. Some authors advocate waiting for the second bleeding before surgery, trying thus to avoid the 30% to 60% initial morbidity and the 15% late morbidity in eloquent areas like the brainstem.
It is clear that early surgery can prevent further episodes of bleeding. On top of that, delayed surgery may increase postoperative morbidity due to the modification of the cleavage plane of dissection over time. A few weeks the after initial bleeding, the cavernoma malformation can be sourrounded by a very easy plane for dissection. In a later stage, a hard-gliotic tissue makes the dissection from nervous tissue riskier ( Fig. 13.2 ). because in this chronic stage after hematoma organization, gliosis is very adherent to normal tissue. This is of great importance at the brainstem and in eloquent supratentorial structures. In summary, the timing for surgery is a factor to be taken into account to avoid postoperative morbidity.
Recurrence of Hemorrhage After Cavernoma Surgery
Recurrence of bleeding after initial surgery is directly related to incomplete previous resection. It is not infrequent that the logical explanation is the difficulty of the area being operated on (i.e., brainstem) and/or the difficulty of the procedure (surgery done on an emergency basis). Obviously, those factors are clearly linked to the surgical technique. Although the global rate of rebleeding in cavernoma surgery is considered very low (less than 1%), when a remnant is left in the surgical field, there is a high probability for rebleeding: 62% of residual lesions will bleed. This is a very important problem because the operation would not achieve its goal: diminishing the probability of further bleeding to zero. Detection of remnants after surgery is of course crucial. In regard to that, recent publications have stated that early postoperative magnetic resonance imaging (MRI) after cavernoma surgery is often hampered by imaging artifacts creating false positive results, therefore rendering the patient ineligible for resection control. However, the reliability of a negative result on an early postoperative T2-weighted MRI is relatively high regarding both cavernomatous malformation and hemosiderin remnants. These considerations have to be taken into account for the appropriate follow-up in cavernoma surgery.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
