gms | German Medical Science

Objective: Surgeries of the temporal region are still generally less well performed than of any other brain lobe, due to the microanatomical, vascular, and functional complexity of the temporal region. A variety of surgical approaches to temporal lobe tumors have been discussed previously. Here, we aimed at developing a novel classification to guide tailored approaches to the respective microanatomical location of temporal lobe tumors.

Methods: Tumors were classified into four main types: lateral (I), polar (II), intrinsic (III) and mesial (IV). Type I and type IV tumors were subcatagorized into A (anterior) and B (posterior to the midmesencephalic line). Based on microanatomical, vascular, and functional anatomy, the following approaches have been suggested: Type I A and B: temporal/transcortical (Type IB on the dominant side with language mapping); Type II: pterional/pretemporal; Type III: pterional/transsylvian/trans-opercular; Type IVA: pterional/transsylvian/transcisternal; Type IVB: supratentorial/infraoccipital (or subtemporal). Based on this classification and categorization of approaches, a prospective series of 105 patients with temporal lobe tumors (76% astrocytomas grades II-IV, 13% metastases, 11% other) were operated. Postoperative (48 hrs post OP) MRI scans to evaluate the extent of resection, and standardized neurological examinations (post OP day 1, day 5, and month 3), including Goldmann perimetries, were undertaken to analyze the classification’s quality as a surgical guideline.

Results: Tumor allocation to one of the four types was always possible. Distribution was: Type A and B: 33, (14 in the dominant hemisphere); Type II: 8; Type III: 30; Type IVA: 21; Type IVB: 7; Type IV A/B (= mixed type): 6. Macroscopic total resection was effected in 88%. Neurological morbidity (transient/ permanent) was: 2/3 new visual field defects; 5/1 third nerve palsies, 2/2 hemipareses, 4/1 aphasia, 1 clinically relevant vasospasm. Surgical morbidity (1 EDH, 2 SDH, 6 wound healing disorders, 2 DVTs) was 9%. The transsylvian approach to limbic and intrinsic tumors avoided destruction of neopallidal functional tissue and white matter tracts, as in lateral corticotomies, and extensive temporal lobe retraction. This approach provided sufficient control over the vessels of the anterior circulation by open visualization.

Conclusions: Implementation of this basic classification results in tailored, safe tumor resection. The presented guideline may prove as a valuable tool for surgical planning.