Mesial temporal lobe lesion approaches

Mesial temporal lobe lesion approaches

There are several ways to safely access mesial temporal structures. The transsylvian-transcisternal approach is a good way to access the mesial structures while preserving the lateral and basal temporal structures. Actual lesions associated with epileptogenesis in focal cortical dysplasia (FCD) may be larger than they appear on magnetic resonance imaging. For this reason, evaluations to locate sufficient epileptogenic foci, including invasive studies, should be completed for FCD, and epilepsy surgery should be performed according to these results. Regardless, the ultimate goal of all epilepsy surgeries is to maximize seizure control while maintaining neurological function. Therefore, a tailored approach based on the properties of the lesion is needed1).

For Campero et al., dividing the mesial temporal region (MTR) into 3 regions allows us to adapt the approach to lesion location. Thus, the anterior sector can be approached via the sylvian fissure, the middle sector can be approached transtemporally, and the posterior sector can be approached via the supracerebellar approach 2).

There are limited reports on the transcortical approach for the resection of tumors within this region.

Morshed et al., from the UCSF Medical Center, described the technical considerations and functional outcomes in patients undergoing transcortical resection of gliomas of the mesial temporal lobe (MTL).

Patients 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.

Fifty 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 classification 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.

Mesial 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 3).


Microsurgery was performed via transsylviantranstemporal, or subtemporal approaches on 62 patients with mesial temporal lobe gliomas, 33 with localized tumors within the mesial temporal structures (type A), 19 in anterior portion (type A1), and 14 extending to posterior portion (type A2); 19 patients with multicompartmental tumors involving the mesial temporal lobe, insular lobe, and posterior frontorbital gurus (type B); 14 patients with tumors involving the temporal pole and lateral areas of the temporal horn (type C); and 6 patients with tumors infiltrating the brain stem, basal nuclei and thalamus (type D).

Trans-sylvian approach was performed in 25 cases of which total tumor removal was achieved in 14 cases, subtotal removal in 6 cases, and gross removal in 5 cases. Primary visual deficits worsened after surgery in 5 cases. Trans-temporal approach was used in 23 cases of which total tumor resection was achieved in 15 cases, subtotal resection in 5 cases, and gross resection in 3 cases. Primary visual deficits worsened after surgery in 5 cases. Four patients in which preoperative vision were good presented with visual deficits postoperatively. Subtemporal approach was used in 14 cases of which total tumor removal was achieved in 10 cases, and subtotal removal in 4 cases. All 14 patients did not develop worsened vision after surgery.

Trans-sylvian and subtemporal approaches can reduce possible harm to parenchyma and optic radiation, whereas approaches to the temporal horn through the superior and middle temporal gyri will induce damage to parenchyma and optic radiation 4).


The aim of Faust et al., was to categorize temporal lobe tumors based on anatomical, functional, and vascular considerations and to devise a systematic field manual of surgical approaches.

Tumors were classified into four main types with assigned approaches: Type I-lateral: transcortical; type II-polar: pterional/transcortical; type III-central: transsylvian/transopercular; 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.

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 5).


Twenty formalin-fixed, adult cadaveric specimens were studied. Ten brains provided measurements to compare different surgical strategies. Approaches were demonstrated using 10 silicon-injected cadaveric heads. Surgical cases were used to illustrate the results by the different approaches. Transverse lines at the level of the inferior choroidal point and quadrigeminal plate were used to divide the medial temporal region into anterior, middle, and posterior portions. Surgical approaches to the medial temporal region were classified into four groups: superior, lateral, basal, and medial, based on the surface of the lobe through which the approach was directed. The approaches through the medial group were subdivided further into an anterior approach, the transsylvian transcisternal approach, and two posterior approaches, the occipital interhemispheric and supracerebellar transtentorial approaches.

The anterior portion of the medial temporal region can be reached through the superior, lateral, and basal surfaces of the lobe and the anterior variant of the approach through the medial surface. The posterior group of approaches directed through the medial surface are useful for lesions located in the posterior portion. The middle part of the medial temporal region is the most challenging area to expose, where the approach must be tailored according to the nature of the lesion and its extension to other medial temporal areas.

Each approach to medial temporal lesions has technical or functional drawbacks that should be considered when selecting a surgical treatment for a given patient. Dividing the medial temporal region into smaller areas allows for a more precise analysis, not only of the expected anatomic relationships, but also of the possible choices for the safe resection of the lesion. The systematization used here also provides the basis for selection of a combination of approaches 6).


Germano described a transsulcal temporal approach to mesiotemporal lesions and its application in three patients. Gross-total resection of the lesion was accomplished in all cases. An anatomical cadaveric study was also performed to delineate the microsurgical anatomy of this approach. Precise knowledge of temporal intraventricular landmarks allows navigation to the lesion without the need for a navigational system. This approach is helpful for neurologically intact patients with mesiotemporal lesions 7).

References

1)

Chong S, Phi JH, Lee JY, Kim SK. Surgical Treatment of Lesional Mesial Temporal Lobe Epilepsy. J Epilepsy Res. 2018 Jun 30;8(1):6-11. doi: 10.14581/jer.18002. eCollection 2018 Jun. Review. PubMed PMID: 30090756; PubMed Central PMCID: PMC6066696.
2)

Campero A, Ajler P, Rica C, Rhoton A Jr. Cavernomas and Arteriovenous Malformations in the Mesial Temporal Region: Microsurgical Anatomy and Approaches. Oper Neurosurg (Hagerstown). 2017 Feb 1;13(1):113-123. doi: 10.1227/NEU.0000000000001239. PubMed PMID: 28931254.
3)

Morshed RA, Young JS, Han SJ, Hervey-Jumper SL, Berger MS. The transcortical equatorial approach for gliomas of the mesial temporal lobe: techniques and functional outcomes. J Neurosurg. 2018 Apr 20:1-9. doi: 10.3171/2017.10.JNS172055. [Epub ahead of print] PubMed PMID: 29676697.
4)

Jiang ZL, Wang ZC, Jiang T. [Surgical outcomes of different approaches for mesial temporal lobe gliomas]. Zhonghua Yi Xue Za Zhi. 2005 Sep 7;85(34):2428-32. Chinese. PubMed PMID: 16321253.
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Faust K, Schmiedek P, Vajkoczy P. Approaches to temporal lobe lesions: a proposal for classification. Acta Neurochir (Wien). 2014 Feb;156(2):409-13. doi: 10.1007/s00701-013-1917-4. Epub 2013 Nov 8. Review. PubMed PMID: 24201756.
6)

Campero A, Tróccoli G, Martins C, Fernandez-Miranda JC, Yasuda A, Rhoton AL Jr. Microsurgical approaches to the medial temporal region: an anatomical study. Neurosurgery. 2006 Oct;59(4 Suppl 2):ONS279-307; discussion ONS307-8. PubMed PMID: 17041498.
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Germano IM. Transsulcal approach to mesiotemporal lesions. Anatomy, technique, and report of three cases. Neurosurg Focus. 1996 Nov 15;1(5):e4. PubMed PMID: 15099055.

Update: Mesial temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is a chronic neurological condition characterized by recurrent seizures (epilepsy) which originate in the temporal lobe of the brain. The seizures involve sensory changes, for example smelling an unusual odour that is not there, and disturbance of memory.

Mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE-HS) is the most common type of focal epilepsy.

Etiology

The most common cause is mesial temporal sclerosis.
Water homeostasis has been shown crucial for regulation of neuronal excitability. The control of water movement is achieved through a family of small integral membrane channel proteins called aquaporins (AQPs). Despite the fact that changes in water homeostasis occur in sclerotic hippocampi of people with temporal lobe epilepsy (TLE) , the expression of AQPs in the epileptic brain is not fully characterised 1).
Soluble human epoxide hydrolase 2 is increased in both lateral and medial temporal tissues in temporal lobe epilepsy. Further studies should be conducted as inhibition of this enzyme has resulted in a significant decrease in or stopping of seizures and attenuated neuro-inflammation in experimental epilepsy models in the current literature 2).

Pathophysiology

In order to understand the pathophysiology of temporal lobe epilepsy (TLE), and thus to develop new pharmacological treatments, in vivo animal models that present features similar to those seen in TLE patients have been developed during the last four decades. Some of these models are based on the systemic administration of chemoconvulsants to induce an initial precipitating injury (status epilepticus) that is followed by the appearance of recurrent seizures originating from limbic structures.
Kainic acid and pilocarpine models, have been widely employed in basic epilepsy research. Their behavioral, electroencephalographic and neuropathologic features and response of these models to antiepileptic drugs and the impact they might have in developing new treatments are explained in the work of Lévesque et al. 3).


The transition to the ictal stage is accompanied by increasing global synchronization and a more ordered spectral content of the signals, indicated by lower spectral entropy. The interictal connectivity imbalance (lower ipsilateral connectivity) is sustained during the seizure, irrespective of any appreciable imbalance in the spectral entropy of the mesial recordings 4).

Diagnosis

Fractional anisotropy asymmetry (FAA) values can be potentially used to identify the seizures of origin of TLE and to help understand the relationship between fiber tracts with the side of seizure origin of TLE 5).
The area of predominant perifocal 18F positron emission tomography hypometabolism and reduced [11C]flumazenil (11C-FMZ) -binding on PETscans is currently considered to contain the epileptogenic zone and corresponds anatomically to the area localizing epileptogenicity in patients with temporal lobe epilepsy (TLE).

Complicactions

Drug resistant epilepsy is a major clinical challenge affecting about 30% of temporal lobe epilepsy (TLE) patients.
The reasons for failure of surgical treatment for mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS) remain unclear.

Treatment

Surgery

see Temporal lobe epilepsy surgery.
Surgical resection is the gold standard treatment for drug-resistant focal epilepsy, including mesial temporal lobe epilepsy (MTLE) and other focal cortical lesions with correlated electrophysiological features.
Surgical approaches for medically refractory mesial temporal lobe epilepsy (MTLE) that previously have been reported include anterior temporal lobectomy (ATL), transcortical selective amygdalohippocampectomy, transsylvian amygdalohippocampectomy, and subtemporal amygdalohippocampectomy.
Each approach has its advantages and potential pitfalls.

Anterior temporal lobectomy

Outcome

The extent of pre-surgical perifocal PET abnormalities, the extent of their resection, and the extent of non-resected abnormalities were not useful predictors of individual freedom from seizures in patients with TLE 6).

Case series

2017

Seizure, cognitive, and psychiatric outcomes were reviewed after 389 surgeries performed between 1990 and 2015 on patients aged 15-67 years at a tertiary center. Three surgical approaches were used: anterior temporal lobectomy (ATL; n = 209), transcortical selective amygdalohippocampectomy (SAH; n = 144), and transsylvian SAH (n = 36).
With an average follow-up of 8.7 years (range = 1.0-25.2), seizure outcome was classified as Engel I in 83.7% and Engel Ia in 57.1% of patients. The histological classification of HS was type 1 for 75.3% of patients, type 2 for 18.7%, and type 3 for 1.2%. Two factors were significantly associated with seizure recurrence: past history of status epilepticus and preoperative intracranial electroencephalographic recording. In contrast, neither HS type, the presence of a dual pathology, nor surgical approach was associated with seizure outcome. Risk of cognitive impairment was 3.12 (95% confidence interval = 1.27-7.70), greater in patients after ATL than in patients after transcortical SAH. A presurgical psychiatric history and postoperative cognitive impairment were associated with poor psychiatric outcome.
The SAH and ATL approaches have similar beneficial effects on seizure control, whereas transcortical SAH tends to minimize cognitive deterioration after surgery. Variation in postsurgical outcome with the class of HS should be investigated further 7).

2016

A certain number of patients suffer significant decline in verbal memory after hippocampectomy. To prevent this disabling complication, a reliable test for predicting postoperative memory decline is greatly desired. Therefore, Tani et al., assessed the value of electrical stimulation of the parahippocampal gyrus (PHG) as a provocation test of verbal memory decline after hippocampectomy on the dominant side.
Eleven right-handed, Japanese-speaking patients with medically intractable left temporal lobe epilepsy (TLE) participated in the study. Before surgery, they underwent provocative testing via electrical stimulation of the left PHG during a verbal encoding task. Their pre- and posthippocampectomy memory function was evaluated according to the Wechsler Memory Scale-Revised (WMS-R) and/or Mini-Mental State Examination (MMSE) before and 6 months after surgery. The relationship between postsurgical memory decline and results of the provocative test was evaluated.
Left hippocampectomy was performed in 7 of the 11 patients. In 3 patients with a positive provocative recognition test, verbal memory function, as assessed by the WMS-R, decreased after hippocampectomy, whereas in 4 patients with a negative provocative recognition test, verbal memory function, as assessed by the WMS-R or MMSE, was preserved.
Results of the present study suggest that electrical stimulation of the PHG is a reliable provocative test to predict posthippocampectomy verbal memory decline 8).

2001

Eighty patients with temporal lobe epilepsy were randomly assigned to surgery (40 patients) or treatment with antiepileptic drugs for one year (40 patients). Optimal medical therapy and primary outcomes were assessed by epileptologists who were unaware of the patients’ treatment assignments. The primary outcome was freedom from seizures that impair awareness of self and surroundings. Secondary outcomes were the frequency and severity of seizures, the quality of life, disability, and death.
At one year, the cumulative proportion of patients who were free of seizures impairing awareness was 58 percent in the surgical group and 8 percent in the medical group (P<0.001). The patients in the surgical group had fewer seizures impairing awareness and a significantly better quality of life (P<0.001 for both comparisons) than the patients in the medical group. Four patients (10 percent) had adverse effects of surgery. One patient in the medical group died.
In temporal-lobe epilepsy, surgery is superior to prolonged medical therapy. Randomized trials of surgery for epilepsy are feasible and appear to yield precise estimates of treatment effects 9).
1)

Salman MM, Sheilabi MA, Bhattacharyya D, Kitchen P, Conner AC, Bill RM, Woodroofe MN, Conner MT, Princivalle AP. Transcriptome analysis suggests a role for the differential expression of cerebral aquaporins and the MAPK signalling pathway in human temporal lobe epilepsy. Eur J Neurosci. 2017 Jul 17. doi: 10.1111/ejn.13652. [Epub ahead of print] PubMed PMID: 28715131.
2)

Ahmedov ML, Kemerdere R, Baran O, Inal BB, Gumus A, Coskun C, Yeni SN, Eren B, Uzan M, Tanriverdi T. Tissue Expressions of Soluble Human Epoxide Hydrolase-2 Enzyme in Patients with Temporal Lobe Epilepsy. World Neurosurg. 2017 Jun 29. pii: S1878-8750(17)31032-X. doi: 10.1016/j.wneu.2017.06.137. [Epub ahead of print] PubMed PMID: 28669871.
3)

Lévesque M, Avoli M, Bernard C. Animal Models of temporal Lobe Epilepsy Following Systemic Chemoconvulsant Administration. J Neurosci Methods. 2015 Mar 10. pii: S0165-0270(15)00091-6. doi: 10.1016/j.jneumeth.2015.03.009. [Epub ahead of print] PubMed PMID: 25769270.
4)

Vega-Zelaya L, Pastor J, de Sola RG, Ortega GJ. Disrupted Ipsilateral Network Connectivity in Temporal Lobe Epilepsy. PLoS One. 2015 Oct 21;10(10):e0140859. doi: 10.1371/journal.pone.0140859. eCollection 2015. PubMed PMID: 26489091.
5)

Li H, Xue Z, Dulay MF Jr, Verma A, Karmonik C, Grossman RG, Wong ST. Fractional anisotropy asymmetry and the side of seizure origin for partial onset-temporal lobe epilepsy. Comput Med Imaging Graph. 2014 Jul 2. pii: S0895-6111(14)00102-5. doi: 10.1016/j.compmedimag.2014.06.009. [Epub ahead of print] PubMed PMID: 25037096.
6)

Stanišić M, Coello C, Ivanović J, Egge A, Danfors T, Hald J, Heminghyt E, Mikkelsen MM, Krossnes BK, Pripp AH, Larsson PG. Seizure outcomes in relation to the extent of resection of the perifocal fluorodeoxyglucose and flumazenil PET abnormalities in anteromedial temporal lobectomy. Acta Neurochir (Wien). 2015 Sep 8. [Epub ahead of print] PubMed PMID: 26350516.
7)

Mathon B, Bielle F, Samson S, Plaisant O, Dupont S, Bertrand A, Miles R, Nguyen-Michel VH, Lambrecq V, Calderon-Garcidueñas AL, Duyckaerts C, Carpentier A, Baulac M, Cornu P, Adam C, Clemenceau S, Navarro V. Predictive factors of long-term outcomes of surgery for mesial temporal lobe epilepsy associated with hippocampal sclerosis. Epilepsia. 2017 Jun 28. doi: 10.1111/epi.13831. [Epub ahead of print] PubMed PMID: 28656696.
8)

Tani N, Kishima H, Khoo HM, Yanagisawa T, Oshino S, Maruo T, Hosomi K, Hirata M, Kazui H, Nomura KT, Aly MM, Kato A, Yoshimine T. Electrical stimulation of the parahippocampal gyrus for prediction of posthippocampectomy verbal memory decline. J Neurosurg. 2016 Nov;125(5):1053-1060. PubMed PMID: 26771851.
9)

Wiebe S, Blume WT, Girvin JP, Eliasziw M; Effectiveness and Efficiency of Surgery for Temporal Lobe Epilepsy Study Group. A randomized, controlled trial of surgery for temporal-lobe epilepsy. N Engl J Med. 2001 Aug 2;345(5):311-8. PubMed PMID: 11484687.
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