Contralateral anterior interhemispheric-transcallosal-transrostral approach to the subcallosal region: a novel surgical technique.

OBJECTIVE The authors report a novel surgical route from a superior anatomical aspect-the contralateral anterior interhemispheric-transcallosal-transrostral approach-to a lesion located in the subcallosal region. The neurosurgical approach to the subcallosal region is challenging due to its deep location and close relationship with important vascular structures. Anterior and inferior routes to the subcallosal region have been described but risk damaging the branches of the anterior cerebral artery. METHODS Three formalin-fixed and silicone-injected adult cadaveric heads were studied to demonstrate the relationships between the transventricular surgical approach and the subcallosal region. The surgical, clinical, and radiological history of a 39-year-old man with a subcallosal cavernous malformation was retrospectively used to document the neurological examination and radiographic parameters of such a case. RESULTS The contralateral anterior interhemispheric-transcallosal-transrostral approach provides access to the subcallosal area that also includes the inferior portion of the pericallosal cistern, lamina terminalis cistern, the paraterminal and paraolfactory gyri, and the anterior surface of the optic chiasm. The approach avoids the neurocritical perforating branches of the anterior communicating artery. CONCLUSIONS The contralateral anterior interhemispheric-transcallosal-transrostral approach may be an alternative route to subcallosal area lesions, with less risk to the branches of the anterior cerebral artery, particularly the anterior communicating artery perforators.

Recruitment of Contralateral Supplementary Motor Area in Functional Recovery Following Medial Frontal Lobe Surgery: An fMRI Case Study.

BACKGROUND AND OBJECTIVE: Supplementary motor area (SMA) syndrome, an executive disorder with motor and speech dysfunctions, is rather unpredictable with typically a complete or almost complete functional recovery within weeks or months. Compensatory mechanisms are associated with contralateral cortical recruitment of the lateral premotor circuitry. We sought to investigate the role of healthy SMA for motor recovery following surgery in the medial frontal lobe. METHODS: A 48-year-old right-handed man presented with focal motor seizures. The diagnostic work-up revealed a low-grade glioma at the superior frontal gyrus. The patient was operated on with intraoperative monitoring of motor pathways, and resection was taken to the functional boundaries. RESULTS: Postoperatively, the patient experienced a typical SMA syndrome that almost completely resolved in the long term. Motor recovery occurred concurrently with a shift of SMA activation to the healthy hemisphere together with an increased lateral premotor circuitry, especially for the hand map. CONCLUSION: Our results confirm brain remodeling of the lateral premotor cortex, as previously described, and indicate that functional improvement is also paralleled with a shift of SMA activation toward the healthy hemisphere.

Semantic strategy training increases memory performance and brain activity in patients with prefrontal cortex lesions.

OBJECTIVE: Memory deficit is a frequent cognitive disorder following acquired prefrontal cortex lesions. In the present study, we investigated the brain correlates of a short semantic strategy training and memory performance of patients with distinct prefrontal cortex lesions using fMRI and cognitive tests. METHODS: Twenty-one adult patients with post-acute prefrontal cortex (PFC) lesions, twelve with left dorsolateral PFC (LPFC) and nine with bilateral orbitofrontal cortex (BOFC) were assessed before and after a short cognitive semantic training using a verbal memory encoding paradigm during scanning and neuropsychological tests outside the scanner. RESULTS: After the semantic strategy training both groups of patients showed significant behavioral improvement in verbal memory recall and use of semantic strategies. In the LPFC group, greater activity in left inferior and medial frontal gyrus, precentral gyrus and insula was found after training. For the BOFC group, a greater activation was found in the left parietal cortex, right cingulated and precuneus after training. CONCLUSION: The activation of these specific areas in the memory and executive networks following cognitive training was associated to compensatory brain mechanisms and application of the semantic strategy.

Prefrontocortical serotonin depletion results in plastic changes of prefrontocortical pyramidal neurons, underlying a greater efficiency of short-term memory.

The prefrontal cortex activity is involved in organizing the short-term memory. Although the involvement of serotonin for an appropriate performance in learning and memory tests is well known, its role is still unclear; as is the cellular basis of short-term memory behavioral performance. Sprague-Dawley rats were stereotactically injected with 1 microg/microl of 5, 7-dihydroxitryptamine to cause a lesion to the dorsal raphe nucleus. Sham-operated or intact rats were also studied as control groups. Before surgery and 20 days post-operatively, each animal was placed in the Biel maze for five consecutive trials. In the pre-treatment test, all three groups decreased significantly the number of errors beginning with the fourth trial. The same occurred in the post-treatment test, except for the experimental group, whose animals committed less errors beginning with the second trial. After behavioral testing, the dorsomedial prefrontal cerebral cortex was dissected out, and the Golgi study of the third-layer pyramidal neurons revealed that the length of both the apical and the basilar dendrites was smaller than that of controls, and that the apical and oblique dendrites had a greater spine density. A major proportion of thin spines was also seen on the basilar and oblique dendrites, and more stubby spines were seen on the apical dendrite. Serotonin depletion in the prefrontal cerebral cortex resulted in cytoarchitectural alterations of the prefrontocortical pyramidal neurons, which may be underlying partially the greater efficiency observed in the short-term memory behavioral performance.

Effects of bilateral ablation or 6-OHDA lesion of the frontal cortex upon the behaviors induced by apomorphine and amphetamine in adult cats.

The main aim of this study was to compare the effects of bilateral 6-OHDA lesion of the prefrontal, frontal and media cerebral cortex, with those of suction ablation of the same areas, upon apomorphine and amphetamine evoked behaviors. Twenty five cats were distributed in four groups: 1) 8 cats received bilateral, injection of 6-OHDA (32 micrograms per hemisphere), and the behaviors elicited by separate injection of apomorphine (2.0 mg/kg s.c.) and amphetamine (2.5 mg/kg s.c.) before and after the lesion were compared; 2) 3 cats received a unilateral injection of 6-OHDA into the cited areas and dopamine concentration on the lesioned site and the contralateral non-lesioned side were compared; 3) 8 cats had bilateral suction ablation of the cited cortical areas and the results of apomorphine and amphetamine evoked behaviors before and after ablation were compared, and 4) the effects of solvent injections and sham operations were studied in 6 additional cats. 6-OHDA lesion had scanty effects on the behaviors evoked by apomorphine and amphetamine. Only two (fear like behavior and lack of food motivation) out of 9 behaviors elicited by apomorphine were modified, while two of five behaviors elicited by amphetamine (immobility and food motivation) showed a change. On the other hand, the ablation procedure had a much wider effect on the behaviors elicited by the dopaminergic agonist drugs. All 5 behaviors evoked by amphetamine were modified, while only 4 of nine behaviors induced by apomorphine did change. These results show the importance of the interplay between dopamine and the target tissue that receive the dopaminergic fibers in the production of the behaviors evoked by parenteral injection of apomorphine and amphetamine.