Microsurgical anatomy and insular connectivity of the cerebral opercula

J Neurosurg 137:1509–1523, 2022

Radiological, anatomical, and electrophysiological studies have shown the insula and cerebral opercula to have extremely high functionality. Because of this complexity, interventions in this region cause higher morbidity compared to those in other areas of the brain. In most early studies of the insula and white matter pathways, insular dissection was begun after the opercula were removed. In this study, the authors examined the insula and deep white matter pathways to evaluate the insula as a whole with the surrounding opercula.

METHODS Twenty formalin-fixed adult cerebral hemispheres were studied using fiber microdissection techniques and examination of sectional anatomy. Dissections were performed from lateral to medial, medial to lateral, inferior to superior, and superior to inferior. A silicone brain model was used to show the normal gyral anatomy. Sections and fibers found at every stage of dissection were photographed with a professional camera. MRI tractography studies were used to aid understanding of the dissections.

RESULTS The relationships between the insula and cerebral opercula were investigated in detail through multiple dissections and sections. The relationship of the extreme and external capsules with the surrounding opercula and the fronto-occipital fasciculus with the fronto-orbital operculum was demonstrated. These findings were correlated with the tractography studies. Fibers of the extreme capsule connect the medial aspect of the opercula with the insula through the peri-insular sulcus. Medial to lateral dissections were followed with the removal of the central core structures, and in the last step, the medial surface of the cerebral opercula was evaluated in detail.

CONCLUSIONS This anatomical study clarifies our understanding of the insula and cerebral opercula, which have complex anatomical and functional networks. This study also brings a new perspective to the connection of the insula and cerebral opercula via the extreme and external capsules.

Epilepsy Surgeries Requiring an Operculoinsular Cortectomy

Neurosurgery 81:602–612, 2017

Epilepsy surgeries requiring an operculoinsulectomy pose significant difficulties because the perisylvian area is highly vascular, deep, and functional.

OBJECTIVE: To report the operative technique and results of epilepsy surgeries requiring an operculoinsular cortectomy at our institution.

METHODS: The data of all consecutive patients who had undergone an epilepsy surgery requiring an operculoinsular cortectomy with a minimum follow-up of 1 yr were reviewed. Tumor and vascular malformation cases were excluded. Surgical techniques are described based on findings during surgery.

RESULTS: Twenty-five patients underwent an epilepsy surgery requiring an operculoinsular cortectomy: mean age at surgery was 35 y (9-51), mean duration of epilepsy was 19 y (5-36), 14were female, and mean duration of follow-up was 4.7 y (1-16).Magnetic resonance imaging of the operculoinsular area was normal or revealed questionable nonspecific findings in 72% of cases. Investigation with intracranial EEG electrodes was done in 17 patients. Surgery was performed on the dominant side for language in 7 patients. An opercular resectionwasperformed inallbut2patientswhoonlyhadan insulectomy.Engel class I seizure control was achieved in 80% of patients. Postoperative neurological deficits (paresis, dysphasia, alteration of taste, smell, hearing, pain, and thermal perceptions) were frequent (75%) but always transient except for 1 patient with persistent mild alteration of thermal and pain perception.

CONCLUSION: Surgical treatment of operculoinsular epilepsy is effective in achieving seizure control and is associated with an acceptable long-term complication rate.

Frontal operculum gliomas: language outcome following resection

Frontal operculum gliomas- language outcome following resection

J Neurosurg 122:725–734, 2015

The dominant hemisphere frontal operculum may contain critical speech and language pathways, and due to these properties, patients with tumors of the opercular region may be at higher risk for postoperative speech dysfunction. However, the likelihood of incurring temporary or permanent language dysfunction is unknown.

Methods The authors retrospectively analyzed their cohort of patients with frontal gliomas to identify those tumors that predominantly involved the dominant frontal operculum. Each tumor was classified as involving the pars orbitalis, pars triangularis, pars opercularis, or a combination of some or all of these areas. The authors then identified and compared characteristics between those patients experiencing transient or permanent speech deficits, as opposed to those with no language dysfunction.

Results Forty-three patients were identified for inclusion in this analysis. Transient deficits occurred in 12 patients (27.9%), while 4 patients (9.8%) had persistent deficits involving language. Individuals with preoperative language deficits and patients with seizures characterized by speech dysfunction appear to be at the highest risk to develop a deficit (relative risks 3.09 and 1.75, respectively). No patient with a tumor involving the pars orbitalis experienced a persistent deficit.

Conclusions Resection of gliomas is widely recognized as a critical element of improved outcome. Given the low rate of language morbidity reported in this group of patients, resection of gliomas within the dominant frontal operculum is well-tolerated with acceptable morbidity and, in this particular location, should not be a deterrent in the overall management of these tumors.