**4. Brain tumor surgery and cognition**

In brain tumors, the first treatment modality is surgery. The aim was to balance the neurolog‐ ical outcomes (minimize the neurological deficits) and oncological outcome [2].

**•** Does brain surgery improve cognitive deficit?

Surgery for brain tumors improves the cognitive function due to the reduction of compres‐ sion as after removal of noninvasive tumors, such as meningiomas, improvement of atten‐ tional function occur [42]. Patients with high-grade glioma have worse cognitive dysfunction than patients with low-grade glioma (LGG) [47]. The worse cognitive deficits in patients with high-grade gliomas have been attributed to higher incidence of intracranial hypertension, the rapid growth, and the infiltrative nature.

Sweet et al. [48] reported that the localization is associated with cognitive effects. Tumors of the pineal region associated with memory impairment, visuospatial function, attention, visuomotor function, problem-solving, and affective disorders.

Medial temporal lobe epilepsy caused by tumor is associated with cognitive deficit (long-term memory dysfunction, difficulties in learning, attention, naming, visuospatial abilities, executive functions, and intelligence) [49].

Less extensive surgery of the mesiotemporal structures correlates with better memory outcome than in the extensive temporal lobe surgery [50].

Verbal memory decline was observed in dominant temporal lobe resection [51], while visuospatial memory decline associated with nondominant temporal lobe resection [52].

Cognitive improvement has been observed after tumor resection, and improvement of verbal memory has been observed after LGG resections in frontal premotor and anterior temporal areas [4], usually after a transient postoperative worsening. This improvement was related to tumor lateralization [53].

Some studies reported postoperative cognitive worsening in (38%) of patients versus 24% rate of improved patients. Worsening associated with executive functions while improvement was observed with memory function. This worsening may correlate to volume of the operated area (tumor size) rather than the location. The postoperative improvement of memory function, the most frequent preoperative cognitive deficit, occurs due to release of the mass effect [54].

Teixidor et al. [4] reported immediate postoperative worsening for working memory in 96% of cases, and Giovagnoli et al. [55] reported that postoperative scores for cognitive tests were not significantly lower than the preoperative.

Talacchi et al. [5] found unexpected low incidence of additional deficits (38%) immediate postoperative and a considerable rate of early improvement (24%), and this correlated with tumor size and histology. This study reported also that postoperative worsening seems to be due to a generic mechanical effect and to manipulation/removal of tumor periphery rather than to discrete focal injury.

Yoshii et al. [53] reported that the cognitive functions in patients with LGG and meningio‐ mas (MGs) in the right brain were normal preoperative and postoperative whereas it de‐ creased preoperative and did not return to the normal scores postoperative in left brain MGs. Temporal and spatial orientation, similarities, first recall, writing, mental reversal decreased after operation.

The explanation of mild cognitive effects in MGs preoperatively is the ability of normal brain tissue to compensate as the slow growth of tumor provides enough time for this compensa‐ tion, but after surgical decompression decline in brain function occurs due to remodeling of normal brain tissue [56]. Another explanation is that extracerebral tumor causes compres‐ sion on brain tissues but local anatomical and functional integrity maintained before surgery.

Stability of cognitive function also was observed after tumor resection, like tumors of third ventricle; the preoperative cognitive impairment in executive function, memory, and fine manual speed did not improve or worsen postoperatively [57].

Postoperative cognitive defects in specific domains were observed, for example, some patients with frontal or precentral tumors showed postoperative minor deterioration in attention [58].

Right prefrontal cortex resection in one study [8] was associated with selective attention impairment (Stroop test performance).
