Limited access inferior temporal gyrus approach to mesial basal temporal lobe tumors

Vascularization of the uncus - Anatomical study and clinical implications

Background:

The objective of this paper was to describe the arterial supply of the uncus and quantify the branches directed to the anteromedial aspect of the human temporal cortex.

Methods:

We studied 150 human cerebral hemispheres identifying main afferent arteries supplying the anteromedial temporal cortex with particular attention to the uncus, determining the territory supplied by each artery through either cortical or perforating branches.

Results:

The uncus was supplied by 419 branches of the anterior choroidal artery (AChA), 210 branches of the internal carotid artery (ICA), 353 branches of the middle cerebral artery (MCA), and 122 branches of the posterior cerebral artery (PCA). The total of supplying vessels was 1104 among the 150 hemispheres studied, which corresponds to 7.36 arteries per uncus. The average of branches per hemisphere was as follows: 2.79 from AChA, 1.40 from ICA, 2.35 from MCA, and 0.81 from PCA. The relative contribution of each artery for the total of specimens studied was as follows: 38% from AChA, 19% from ICA, 32% from the MCA, and 11% from the PCA. We identified cortical anastomoses mostly between the MCA and PCA (27 cases).

Conclusion:

We described and quantified the uncus’ vascularization, including anatomical variations. This updated, detailed description of the mesial temporal vascularization is paramount to improve the treatment of neurosurgical conditions.

Surgery of the amygdala and uncus: a case series of glioneuronal tumors

BACKGROUND

Patients with a lesion within the amygdala and uncus may develop temporal lobe epilepsy despite having functional mesial structures. Resection of functional hippocampus and surrounding structures may lead to unacceptable iatrogenic deficits. To our knowledge, there is limited descriptions of surgical techniques for selectively resecting the amygdala and uncus lesions while preserving the hippocampus in patients with language-dominant temporal lobe pathology.

METHODS

Thirteen patients with language-dominant temporal lobe epilepsy related to amygdala-centric lesions were identified. Patients with sclerosis of the mesial structures or evidence of pathology outside of the amygdala-uncus region were excluded. Neuropsychological evaluation confirmed normal function of the mesial structures ipsilateral to the lesion. All patients were worked up with video-EEG, high-resolution brain MRI, neuro-psychology evaluation, and either Wada or functional MRI testing.

RESULTS

All patients underwent selective resection of the lesion including amygdala and uncus with preservation of the hippocampus via a transcortical inferior temporal gyrus approach to the mesial temporal lobe. Pathology was compatible with glioneuronal tumors. Post-operative MRI demonstrated complete resection in all patients. Eight of the thirteen patients underwent post-operative neuropsychology evaluations and did not demonstrate any significant decline in tasks of delayed verbal recall or visual memory based on the Rey Auditory Verbal Learning Test (RAVLT). One patient showed a slight decrease in confrontation naming using the Boston Naming Test (BNT). Seizure freedom (Engel class I) was achieved in 12 of 13 patients.

CONCLUSION

Selective transcortical amygdala and uncus resection with hippocampus preservation may be a reasonable way to achieve seizure control while sparing functional mesial structures.

Parietal transventricular approach for medial temporal glioma: A technical report

Background:

Medial temporal lobectomy (MTLy) poses a surgical challenge due to convoluted anatomy of medial temporal lobe (MTL). Various approaches have been described to access MTL for removing various pathologies. We, hereby, describe the parietal transventricular approach for removing a concurrent medial temporal glioma in a patient with recurrent parietal glioma.

Case Description:

A 40-year-old female operated and diagnosed case of the right parietal anaplastic astrocytoma presented to us with a recurrence in parietal region. In addition, a fresh lesion was observed in the right MTL suggestive of a separate temporal glioma. The patient underwent excision of both parietal and temporal gliomas through the parietal approach only. Complete excision of parietal recurrence and near-total excision of medial temporal glioma was achieved.

Conclusion:

The parietal approach can be used for excision of medial temporal lesions, especially those involving or extending into its posterior limits. In the presence of concurrent parietal and MTL lesions, both lesions can be removed through a single parietal approach rather than a separate approach for MTLy. It offers additional advantages of the preservation of optic radiations as well as the temporal neocortex. The visual orientation of MTL structures is different when viewed from the parietal approach as compared to the temporal approaches. The parietal approach provides in line orientation of medial temporal structures contrary to the perpendicular orientation visualized in temporal approaches. An understanding of MTL anatomy as viewed from a parietal vantage point and its three-dimensional conceptualization is very important to successfully remove lesions of MTL through the parietal approach.

Are low-grade gliomas of mesial temporal area alone?

Background:

Temporal neocortex which appears normal on magnetic resonance imaging (MRI) may have pathological tissues in low-grade gliomas (LGG) of pure mesial temporal area. Resection of the cortex may be required together with mesial temporal glioma for satisfactory seizure and oncological outcome. The aim of this study was to explore the presence of any pathological tissue on the temporal cortex that appeared normal on preoperative MRI in patients with pure mesial temporal LGGs.

Methods:

This prospective study included 10 patients who underwent surgical resection of temporal lobe for LGG of mesial temporal area. The temporal neocortex with normal appearance on MRI and mesial temporal area were resected separately, and histopathological diagnosis was performed.

Results:

LGGs of the mesial temporal area were diagnosed with glioneuronal tumors in 7 (70%) and low-grade astrocytoma in 2 (20%) patients. Regarding the temporal cortex, gliosis and focal cortical dysplasia were found in 7 (70%) and 2 (20%) patients. In one patient temporal cortex did not contain any pathological tissue. All were seizure-free and no tumor recurrence was noted at the last follow-up.

Conclusion:

Mesial temporal LGGs are not alone and a high proportion of temporal neocortex appeared normal on preoperative MRI, may contain dual pathology. Thus, anterior temporal resection should be performed to have satisfactory seizure and oncological outcomes.

Neuropsychology Outcomes Following Trephine Epilepsy Surgery: The Inferior Temporal Gyrus Approach for Amygdalohippocampectomy in Medically Refractory Mesial Temporal Lobe Epilepsy

BACKGROUND

Surgery is indicated in cases of mesial temporal lobe epilepsy(MTLE) that are refractory to medical management. The inferior temporal gyrus (ITG) approach provides access to the mesial temporal lobe (MTL) structures with minimal tissue disruption. Reported neuropsychology outcomes following this approach are limited.

OBJECTIVE

To report neuropsychological outcomes using an ITG approach to amygdalohippocampectomy (AH) in patients with medically refractory MTLE based on a prospective design.

METHODS

Fifty-four participants had Engel class I/II outcome following resection of MTL using the ITG approach. All participants had localization-related epilepsy confirmed by long-term surface video-electroencephalography and completed pre/postsurgical evaluations that included magnetic resonance imaging (MRI), Wada test or functional MRI, and neuropsychology assessment.

RESULTS

Clinical semiology/video-electroencephalography indicated that of the 54 patients, 28 (52%) had left MTLE and 26 (48%) had right MTLE. Dominant hemisphere resections were performed on 23 patients (43%), nondominant on 31(57%). Twenty-nine (29) had pathology-confirmed mesial temporal sclerosis (MTS). Group level analyses found declines in verbal memory for patients with language-dominant resections (P < .05). No significant decline in neuropsychological measures occurred for patients with MTS. Participants without MTS who underwent a language-dominant lobe resection exhibited a significant decline in verbal and visual memory (P < .05). Nondominant resection participants did not exhibit significant change in neuropsychology scores (P > .05).

CONCLUSION

Neuropsychology outcomes of an ITG approach for selective mesial temporal resection are comparable to other selective AH techniques showing minimal adverse cognitive effects. These data lend support to the ITG approach for selective AH as an option for MTLE.

Clinical Uses of Diffusion Tensor Imaging Fiber Tracking Merged Neuronavigation with Lesions Adjacent to Corticospinal Tract : A Retrospective Cohort Study

OBJECTIVE

To investigate the efficiency of diffusion tensor imaging (DTI) fiber-tracking based neuronavigation and assess its usefulness in the preoperative surgical planning, prognostic prediction, intraoperative course and outcome improvement.

METHODS

Seventeen patients with cerebral masses adjacent to corticospinal tract (CST) were given standard magnetic resonance imaging and DTI examination. By incorporation of DTI data, the relation between tumor and adjacent white matter tracts was reconstructed and assessed in the neuronavigation system. Distance from tumor border to CST was measured.

RESULTS

The sub-portion of CST in closest proximity to tumor was found displaced in all patients. The chief disruptive changes were classified as follows : complete interruption, partial interruption, or simple displacement. Partial interruption was evident in seven patients (41.2%) whose lesions were close to cortex. In the other 10 patients (58.8%), delineated CSTs were intact but distorted. No complete CST interruption was identified. Overall, the mean distance from resection border to CST was 6.12 mm (range, 0-21), as opposed to 8.18 mm (range, 2-21) with simple displacement and 2.33 mm (range, 0-5) with partial interruption. The clinical outcomes were analyzed in groups stratified by intervening distances (close, <5 mm; moderated, 5-10 mm; far, >10 mm). For the primary brain tumor patients, the proportion of completely resected tumors increased progressively from close to far grouping (42.9%, 50%, and 100%, respectively). Five patients out of seven (71.4%) experienced new neurologic deficits postoperatively in the close group. At meantime, motor deterioration was found in six cases in the close group. All patients in the far and moderate groups received excellent (modified Rankin Scale [mRS] score, 0-1) or good (mRS score, 2-3) rankings, but only 57.1% of patients in the close group earned good outcome scores.

CONCLUSION

DTI fiber tracking based neuronavigation has merit in assessing the relation between lesions and adjacent white matter tracts, allowing prediction of patient outcomes based on lesion-CST distance. It has also proven beneficial in formulating surgical strategies.

The transcortical equatorial approach for gliomas of the mesial temporal lobe: techniques and functional outcomes

OBJECTIVEMany surgical approaches have been described for lesions within the mesial temporal lobe (MTL), but there are limited reports on the transcortical approach for the resection of tumors within this region. Here, the authors describe the technical considerations and functional outcomes in patients undergoing transcortical resection of gliomas of the MTL.METHODSPatients with a glioma (WHO grades I-IV) located within the MTL who had undergone the transcortical approach in the period between 1998 and 2016 were identified through the University of California, San Francisco (UCSF) tumor registry and were classified according to tumor location: preuncus, uncus, hippocampus/parahippocampus, and various combinations of the former groups. Patient and tumor characteristics and outcomes were determined from operative, radiology, pathology, and other clinical reports that were available through the UCSF electronic medical record.RESULTSFifty patients with low- or high-grade glioma were identified. The mean patient age was 46.8 years, and the mean follow-up was 3 years. Seizures were the presenting symptom in 82% of cases. Schramm types A, C, and D represented 34%, 28%, and 38% of the tumors, and the majority of lesions were located at least in part within the hippocampus/parahippocampus. For preuncus and preuncus/uncus tumors, a transcortical approach through the temporal pole allowed for resection. For most tumors of the uncus and those extending into the hippocampus/parahippocampus, a corticectomy was performed within the middle and/or inferior temporal gyri to approach the lesion. To locate the safest corridor for the corticectomy, language mapping was performed in 96.9% of the left-sided tumor cases, and subcortical motor mapping was performed in 52% of all cases. The mean volumetric extent of resection of low- and high-grade tumors was 89.5% and 96.0%, respectively, and did not differ by tumor location or Schramm type. By 3 months' follow-up, 12 patients (24%) had residual deficits, most of which were visual field deficits. Three patients with left-sided tumors (9.4% of dominant-cortex lesions) experienced word-finding difficulty at 3 months after resection, but 2 of these patients demonstrated complete resolution of symptoms by 1 year.CONCLUSIONSMesial temporal lobe gliomas, including larger Schramm type C and D tumors, can be safely and aggressively resected via a transcortical equatorial approach when used in conjunction with cortical and subcortical mapping.

Middle Temporal Gyrus Versus Inferior Temporal Gyrus Transcortical Approaches to High-Grade Astrocytomas in the Mediobasal Temporal Lobe: A Comparison of Outcomes, Functional Restoration, and Surgical Considerations

INTRODUCTION

High-grade astrocytomas of the mesial temporal lobe may pose surgical challenges. Several approaches (trans-sylvian, subtemporal, and transcortical) have been designed to circumnavigate the critical neurovascular structures and white fiber tracts that surround this area. Considering the paucity of literature on the transcortical approach for these lesions, we describe our institutional experience with transcortical approaches to Grade III/IV astrocytomas in the mesial temporal lobe.

METHODS

Between 1999 and 2009, 23 patients underwent surgery at the Johns Hopkins Medical Institutions for Grade III/IV astrocytomas involving the mesial temporal lobe (without involvement of the temporal neocortex). Clinical notes, operative records, and imaging were reviewed.

RESULTS

Thirteen patients had tumors in the dominant hemisphere. All patients underwent surgery via a transcortical approach (14 via the inferior temporal gyrus and 9 via the middle temporal gyrus). Gross total resection was obtained in 92 % of the cohort. Neurological outcomes were: clinically significant stroke (2 patients), new visual deficits (2 patients), new speech deficit (1 patient); seizure control (53 %).

CONCLUSIONS

In comparison to reported results in the literature for the transylvian and subtemporal approaches, the transcortical approach may provide the access necessary for a gross total resection with minimal neurological consequences. In our series of patients, there was no statistically significant difference in outcomes between the middle temporal gyrus versus the inferior temporal gyrus trajectories.

Temporal lobe epilepsy and cavernous malformations: surgical strategies and long-term outcomes

OBJECTIVE

Cerebral cavernous malformations (CCM) of the temporal lobe often present with seizures. Surgical resection of these lesions can offer durable seizure control. There is, however, no universally accepted methodology for assessing and surgically treating these patients. We propose an algorithm to maximize positive surgical outcomes (seizure control) while minimizing post-surgical neurological deficit.

METHODS

A retrospective review of 34 patients who underwent epilepsy surgery for radiographically proven temporal lobe CCM was conducted. Patients underwent a relatively standard work-up for seizure localization. In patients with mesial temporal lobe epilepsy (MTLE), a complete resection of the epileptogenic zone was performed including amygdalo-hippocampectomy in addition to a lesionectomy if not contraindicated by pre-operative work-up. Patients with neocortical epilepsy underwent intraoperative electrocorticography (ECoG)-guided lesionectomy.

RESULTS

Seizure-free rate for mesial and neocortical (anterior, lateral, and basal) location was 90 vs. 83 %, respectively. Complete resection of the lesion, irrespective of location, was statistically significant for seizure control (p = 0.018). There was no difference in seizure control based on disease duration or location (p > 0.05). Patients with mesial temporal CCM who presented with MTLE were presumed to also have mesial temporal sclerosis (MTS), or dual pathology. These patients underwent routine resection of the mesial structures. Interestingly, patients who had MTLE and basal (neocortical) lesions who underwent a mesial resection for suspected MTS were found not to have dual pathology.

CONCLUSIONS

Patients with temporal lobe CCM should be offered resection for durable seizure control, prevention of secondary epileptogenic foci, and elimination of hemorrhage risk. The preoperative work-up should follow a team approach. Surgical intervention should include complete lesionectomy in all cases. Intra or extra-operative ECoG for neocortical lesions may be beneficial. Management of mesial temporal CCMs (archicortex) should consider resection of a well-defined epileptogenic zone (including mesial structures) due to high probability of pathologically proven MTS. The use of this treatment algorithm is useful for the education and treatment of these patients.

Approaches to temporal lobe lesions: a proposal for classification

BACKGROUND

Tumor surgery in the temporal region is challenging due to anatomical complexity and the versatility of surgical approaches. The aim was to categorize temporal lobe tumors based on anatomical, functional, and vascular considerations and to devise a systematic field manual of surgical approaches.

METHODS

Tumors were classified into four main types with assigned approaches: Type I-lateral: transcortical; type II-polar: pterional/transcortical; type III-central: transsylvian/trans-opercular; type IV-mesial: transsylvian/trans-cisternal if more anterior (=Type IV A), and supratentorial/infraoccipital if more posterior (=type IV B). 105 patients have been operated on prospectively using the advocated guidelines. Outcomes were evaluated.

CONCLUSION

Systematic application of the proposed classification facilitated a tailored approach, with gross total tumor resection of 88 %. Neurological and surgical morbidity were less than 10 %. The proposed classification may prove a valuable tool for surgical planning.

Using the zygomatic root as a reference point in temporal lobe surgery

BACKGROUND

The zygomatic root (ZR) is an anatomic landmark routinely identified during cranial procedures. Traditionally, it has been used for identification of structures other than temporal lobe anatomy. The aim of this study was to define the structural relationship between the ZR and temporal lobe anatomy and provide a consistent landmark to guide surgical dissection. To our knowledge, there have been no studies demonstrating this relationship.

METHODS

Eighteen DICOM series were analyzed. 2 mm axial MRI slices were reconstructed with the x-axis centered along the zygoma. The posterior point of the ZR that marks the beginning of the groove between the zygoma and temporal bone was identified on all images. Several measures were taken to quantify the relationship of the zygomatic root to surgical landmarks used during temporal lobe surgery.

RESULTS

The inferior temporal gyrus was always found just medial to the ZR. The mean distance between the ZR and temporal pole was 2.75 cm on the right and 2.78 cm on the left. The tip of the temporal horn was located on average 2.4 cm (left) and 2.31 cm (right) medial to the ZR. The tip of the temporal horn was found to be an average distance of 1 mm (left and right) posterior and 1.34 cm (left and right) superior to the ZR. All distances were measured orthogonally for each of the x, y, and z axes.

CONCLUSION

The zygomatic root is an easily identifiable and consistent bony landmark that can serve as an adjuvant to neuronavigation for identification of temporal lobe surgical anatomy.

Complications after mesial temporal lobe surgery via inferiortemporal gyrus approach

Object

The purpose of this study was to identify the complications associated with the inferior temporal gyrus approach to anterior mesial temporal lobe resection for temporal lobe epilepsy.

Methods

This retrospective study examined complications experienced by 483 patients during the 3 months after surgery. All surgeries were performed during 1998–2012 by the senior author (F.L.V.).

Results

A total of 13 complications (2.7%) were reported. Complications were 8 delayed subdural hematomas (1.6%), 2 superficial wound infections (0.4%), 1 delayed intracranial hemorrhage (0.2%), 1 small lacunar stroke (0.2%), and 1 transient frontalis nerve palsy (0.2%). Three patients with subdural hematoma (0.6%) required readmission and surgical intervention. One patient (0.2%) with delayed intracranial hemorrhage required readmission to the neuroscience intensive care unit for observation. No deaths or severe neurological impairments were reported. Among the 8 patients with subdural hematoma, 7 were older than 40 years (87.5%); however, this finding was not statistically significant (p = 0.198).

Conclusions

The inferior temporal gyrus approach to mesial temporal lobe resection is a safe and effective method for treating temporal lobe epilepsy. Morbidity and mortality rates associated with this procedure are lower than those associated with other neurosurgical procedures. The finding that surgical complications seem to be more common among older patients emphasizes the need for early surgical referral of patients with medically refractory epilepsy.

Long-term radiosurgery effects in the treatment of temporal lobe epilepsy

Epilepsy surgery is an effective treatment for medically resistant temporal lobe epilepsy (TLE). To minimize complication rates and potentially improve neuropsychology outcomes, stereotactic radiosurgery (SRS) has been explored as an alternative. Two pilot trials have demonstrated the effectiveness of SRS for the treatment of medically resistant TLE, with seizure-free outcomes for approximately 65% of patients at last follow-up. Despite encouraging results, no conclusive long-term outcomes are available for SRS. This article discusses a single patient who presented with recurrent seizures, worsening headaches, and persistent abnormal MRI findings 7 years and 8 months after SRS.

This 29-year-old woman with a history of medically refractory complex partial seizures since childhood was referred for evaluation. Medical management had failed in this patient. The workup was compatible with left mesial temporal lobe onset, with MRI findings suggestive of mesial temporal sclerosis. In 2003, at the age of 23 years, she underwent Gamma Knife surgery (GKS) targeting the left temporal mesial area with a dose of 24 Gy at the 50% marginal isodose line. After GKS, the patient's seizures decreased in frequency over several months, but auras were persistent. Nine months after treatment, she developed worsening headaches. A follow-up MRI study demonstrated a thick, irregular, enhancing lesion in the medial part of the temporal lobe. She was placed on corticosteroids, with resolution of her headaches.

Her seizures and headaches recurred in March 2010. An MRI study showed a 2.2-cm, ill-defined, enhancing cystic lesion in the left mesial temporal lobe with T2 and FLAIR hyperintensity, which was presumably radiation induced. At that time, the patient opted for left temporal lobe resection to control her seizures. Histological examination showed moderately severe, remote, longstanding sclerosis at the level of the hippocampus. A vascular lesion was identified, and it was most consistent with radiation-induced capillary hemangioma. The entorhinal region was severely damaged, with hemorrhage, necrosis, neuronal loss, astrogliosis, and hemosiderin deposition. There was evidence of radiation vasculopathy.

Radiation-induced lesions after SRS for the treatment of epilepsy are not well documented. Although GKS is a promising technique for the treatment of medically resistant TLE, the ideal candidate is not yet well defined. The selection of the appropriate technical parameters to obtain a desirable functional effect without histological damage to the surrounding neural tissue remains a challenge. This case illustrates the need for long-term follow-up when radiosurgery is used for epilepsy.

Interhemispheric approach to tumors of the posterior gyrus cinguli

OBJECTIVE

Posterior gyrus cinguli tumors are a well-defined group of tumors that pose considerable challenges in creating surgical access and manipulating adjacent eloquent areas (visual and motor). Here we report our 5-year experience in the surgical treatment of these tumors and describe tumor characteristics, surgical steps, critical aspects, and prognostic factors.

METHODS

This series comprises 37 patients operated on for glioma (high-grade in 28, low-grade in 9), often presenting with motor impairment (n=20), intracranial hypertension (n=15), seizures (n=11), and/or hemianopia (n=9). Preoperative assessment was performed with magnetic resonance imaging. Half of the tumors were more than 4 cm in size, and the majority presented secondary extension into the fronto-parieto-occipital area, the temporo-mesial area, and/or the corpus callosum. Positioning and assisted surgery were optimized in each patient based on preoperative planning.

RESULTS

The ipsilateral interhemispheric approach was elected in all cases. Tumor size and extension were significantly associated with the degree of tumor removal. Total removal was achieved in 25 patients (65%); 4 (10%) had persistent morbidity (visual or motor deficits). The occurrence of local and systemic complications was negligible.

CONCLUSIONS

Surgical treatment of posterior gyrus cinguli tumors can be safely approached via the interhemispheric route as it permits several beneficial operative maneuvers in selected cases.

The place for surgical treatment for AVM involving the temporal lobe

OBJECTIVE

The objective of this study was to analyze preoperative symptoms and late clinical outcomes in patients who underwent surgical treatment of arterio-venous malformations (AVMs) of the temporal lobe, including those involving the Sylvian fissure (SF) and the lateral wall of the inferior ventricular horns-with special respect to postoperative hemiparesis and visual field defects (VFD).

METHODS

Between 1990 and 2007, 44 patients (n = 22 women, n = 22 men) with a mean age of 41 (12-67) years were operated on an AVM of the temporal lobe. All data had been collected prospectively. Patients' charts, as well as surgical reports and outpatient files, were analyzed. Thirteen patients showed an involvement of the SF, and six were localized partially in the lateral wall of the temporal horn. Eight AVMs were located in the temporo-mesial region. Fourteen patients had an AVM located mainly within the visual pathway. In 24 cases, the AVM was located in the dominant hemisphere. The AVMs were classified by the Spetzler-Martin grading system (SM). Visual fields were assessed in all patients pre- and postoperatively by independent ophthalmological examiners.

RESULTS

The initial symptoms leading to the diagnosis of the AVM were seizures in 20 cases (45%), headache without hemorrhage in six cases (14%), incidental finding in five cases (11%), and tinnitus in two cases (5%). Hemorrhage had occurred in 15 cases (34%). Based on SM, 7 AVMs were grade I, 17 grade II, 17 grade III, and 3 grade IV. Preoperatively, seven patients presented with a VFD and two with a hemiparesis. Postoperatively, 8 of 44 (18%) patients presented with a new hemiparesis, remaining permanent in 3 of 44 (7%). In two of these patients, the AVMs were localized temporo-mesially (n = 2/8, 25%). Seven patients (19%) showed a new significant postoperative VFD, and in addition, three patients had worsening of their preexisting VFD (3/7, 43%). Postoperative angiography verified complete AVM occlusion in 43 of 44 (98%) cases. One patient needed reoperation for residual AVM; hence, in all patients, complete occlusion before discharge was achieved.

CONCLUSION

Treatment of temporal lobe AVMs is demanding due to their close spatio-anatomical relationship with important neurovascular structures and the optic radiation. In this surgically treated series, morbidity for a new permanent hemiparesis was 7% and preservation of the visual field could be achieved in almost 90% of all cases. This is a calculable risk for most patients that renders microsurgical resection a justifiable option, even in light of other treatment modalities. The risk for new permanent motor deficits is elevated in temporo-mesial AVMs, and these patients have to be advised accordingly for surgical treatment.

Brain tumors in the mesial temporal lobe: long-term oncological outcome

OBJECT

Surgical treatment of brain tumors in the mesial temporal lobe (MTL) is a highly demanding procedure. Only a few studies describing the surgery of MTL tumors have been reported, and they have been focused on the operative techniques and immediate results of the surgery. The authors have analyzed the long-term oncological outcome in patients with MTL tumors.

METHODS

Thirty-six patients with an MTL tumor were studied. The mean patient age at surgery was 32 years (range 13-62 years). The tumors were confined to the MTL (Schramm Type A) in 25 patients (69%). Extension of the tumor into the fusiform gyrus (Schramm Type C) and temporal stem (Schramm Type D) was observed in 4 and 7 patients (11 and 19%), respectively. There was a significant difference in the tumor size according to Schramm types (p = 0.001). Complete tumor resection was achieved in 26 patients (72%). All tumors were low-grade lesions except for 1 anaplastic astrocytoma.

RESULTS

After a median follow-up period of 50.5 months, 7 patients showed progression of the disease. The actuarial progression-free survival rates were 97% in the 1st year, 84% in the 2nd year, and 80% in the 5th year. The degree of tumor resection was significantly related to the tumor control failure (p < 0.001) and malignant transformation of a low-grade tumor (p < 0.001). Univariate analyses using a Cox proportional hazards model showed that the following factors were significantly associated with a failure to control the tumor: 1) extent of the tumor (Schramm Type D; p = 0.003, relative risk [RR] 12.04); 2) size of the tumor (p = 0.033, RR 1.052/mm); 3) patient age at surgery >or= 50 years (p = 0.007, RR 8.312); and 4) short duration of epilepsy (< 6 months; p = 0.001, RR 21.54).

CONCLUSIONS

Surgery is the principal treatment for MTL tumors, despite its technical difficulty. Complete tumor resection is strongly recommended for long-term tumor control. The MTL tumors are heterogeneous in their prognosis. Older age, short duration of epilepsy, and tumor size are all associated with poor outcome. Patients with these characteristics may have a more aggressive form of the disease than those with MTL tumors associated with chronic epilepsy.