7T Magnetic Resonance Imaging Probabilistic Tractography-Based Evidence of Decussation of the Fibers Between the Lateral Geniculate Nucleus and the Primary Visual Area.

BACKGROUND: Geniculocalcarine fibers are thought to be exclusively ipsilateral. However, recent findings challenged this belief, revealing bilateral recruiting responses in occipitotemporoparietal regions upon unilateral stimulation of the lateral geniculate nucleus (LGN) in humans. This raised the intriguing possibility of bilateral projections to primary visual areas (V1). This study sought to explore the hypothetical decussation of the geniculocalcarine tract. METHODS: 40 healthy individuals' 7T magnetic resonance images from the Human Connectome Project were examined. Employing MRtrix3 software with the constrained spherical deconvolution algorithm, scans were processed. LGN served as the seed region and contralateral regions of interest (splenium of the corpus callosum, posterior commissure, LGN, V1, pulvinar, and superior colliculus) were defined to reconstruct the hypothetical decussated fibers. Tractography included contralateral V1 as the target region in all segmentations, excluding ipsilateral V1 to eliminate fibers leading to or originating from this area. Additionally, a segmentation of the tract originating from LGN and projecting to the ipsilateral V1 was performed. Mean fraction anisotropy and mean diffusivity metrics were extracted from the density maps. RESULTS: Observations revealed a substantial volume of decussated fibers between LGN and contralateral V1 via the splenium of the corpus callosum, albeit much smaller than ipsilateral fibers. The volume of ipsilateral fibers was similar in both sides. Left LGN-originating decussated fibers were more than double those originating from the right LGN. Tract segmentation to other regions of interests yielded no fibers. CONCLUSIONS: This study suggests a partial decussation of the fibers between LGN and V1, likely constituting the geniculocalcarine tract.

A new strategy for treating drug-resistant focal aware seizures: thalamic specific nuclei deep brain stimulation. Illustrative case.

BACKGROUND: Focal aware seizures (FASs) are relatively common and frequently pharmaco-resistant. If the seizure onset zone (SOZ) is in eloquent cortical areas, making resective surgery risky and inadvisable, deep brain stimulation (DBS) of the anterior nucleus of the thalamus, which is efficacious in less than half of the cases, has been the main alternative. New targets should be searched to address this deficiency. The present study aims to determine if DBS of different thalamic specific nuclei can modulate the abnormal electrical activity of the SOZ located in their respective cortical projection areas. Herein, the authors present the first patient in an ongoing trial. OBSERVATIONS: A 60-year-old female patient presented with 25-year history of pharmaco-resistant focal aware visual seizures frequently evolving to focal impaired awareness seizures. The SOZ was in the right occipital lobe (positron emission tomography-computed tomography/video electroencephalography). Magnetic resonance imaging was normal. She underwent ipsilateral lateral geniculate nucleus (LGN) DBS procedure. After a 24-month follow-up, seizure frequency decreased by 97%, improving quality of life and daily functioning without complications. LESSONS: This is the first time the LGN has been targeted in humans. The results support the hypothesis that led to this study. This strategy represents a paradigm shift in the way of treating pharmaco-resistant FASs not amenable to resective surgery.

Bilateral Globus Pallidus Externus Deep Brain Stimulation for the Treatment of Refractory Tourette Syndrome: An Open Clinical Trial.

OBJECTIVES: We have previously proposed that Tourette syndrome (TS) is the clinical expression of the hyperactivity of globus pallidus externus (GPe) and various cortical areas. This study was designed to test this hypothesis by verifying the efficacy and safety of bilateral GPe deep brain stimulation (DBS) for treating refractory TS. MATERIALS AND METHODS: In this open clinical trial, 13 patients were operated on. Target coordinates (center of GPe) were obtained by direct visualization. Physiological mapping was performed with macrostimulation and microrecording. Primary and secondary outcome measures were, respectively, responder and improvement rates of TS and comorbidities, according to pre- and postoperative scores on the following assessment instruments: Yale Global Tic Severity Scale, Yale-Brown Obsessive Compulsive Scale, Beck Depression Inventory/Hamilton Depression Rating Scale, Beck Anxiety Inventory/Hamilton Anxiety Rating Scale, and Concentrated Attention test. RESULTS: Intraoperative stimulation (100 Hz/5.0V) did not produce any adverse effects or impact on tics. Microrecording revealed bursting cells discharging synchronously with tics in the central part of the dorsal half of GPe. Patients were followed up for a mean of 61.46±48.50 months. Responder rates were 76.9%, 75%, 71.4%, 71.4%, and 85.7%, respectively, for TS, obsessive-compulsive disorder (OCD), depression, anxiety, and attention deficit hyperactivity disorder. Mean improvements among responders in TS, OCD, depression, and anxiety were 77.4%, 74.7%, 89%, and 84.8%, respectively. After starting stimulation, tic improvement was usually delayed, taking up to ten days to manifest. Afterward, it increased over time, usually reaching its maximum at approximately one year postoperatively. The best stimulation parameters were 2.3V to 3.0V, 90 to 120 µsec, and 100 to 150 Hz, and the most effective contacts were the two dorsal ones. Two complications were registered: reversible impairment of previous depression and transient unilateral bradykinesia. CONCLUSIONS: Bilateral GPe-DBS proved to be low risk and quite effective for treating TS and comorbidities, ratifying the pathophysiological hypothesis that led to this study. Moreover, it compared favorably with DBS of other targets currently in use.

Ventral intermediate nucleus deep brain stimulation for treatment-resistant focal aware motor seizures: illustrative case.

BACKGROUND: Resection of the seizure onset zone (SOZ) is considered the gold standard for treating refractory focal aware seizures (FASs). When resective surgery is unadvisable, deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT; ANT-DBS) has been the procedure of choice. However, less than half of patients with FASs respond to ANT-DBS. The need for alternative targets to effectively treat FAS is thus evident. OBSERVATIONS: The authors report the case of a 39-year-old woman presenting with pharmaco-resistant focal aware motor seizures, with the SOZ located in the primary motor cortical area. She had previously undergone unsuccessful resection of the left temporoparietal operculum elsewhere. Considering the risk of new resective surgery, she was offered combined ventral intermediate nucleus (Vim)/ANT-DBS. Vim-DBS proved to be superior to ANT-DBS for seizure control (88% vs 32%), although the association of both provided the best results (97%). LESSONS: This is the first report on the use of the Vim as a target of DBS for the treatment of FAS. The excellent results were presumably obtained by modulation of the SOZ through Vim projections to the motor cortex. This opens a completely new avenue for treating FAS: chronic stimulation of specific thalamic nuclei.

Endoscopic endonasal approach for isolated subarachnoid neurocysticercosis in basal cisterns and its complications: illustrative case.

BACKGROUND: Neurocysticercosis (NCC) is an infectious parasitic disease in which humans are the middle host in the life cycle of Taenia solium. It is currently considered to be a neglected tropical disease. According to their location, cysts can cause epilepsy, hydrocephalus, arachnoiditis, and intracranial hypertension. The subarachnoid is the rarest and most morbid form among all forms of NCC presentation. OBSERVATIONS: The authors report an odd case of subarachnoid NCC (SUBNCC). It was treated with expanded endoscopic endonasal surgery. Unfortunately, the patient developed a high-output nasal leak and meningitis after cyst removal, which demanded additional surgical procedures. Nonetheless, the patient showed a good clinical outcome after surgical interventions. LESSONS: Endoscopic endonasal approach of SUBNCC can be safe and curative. Neverthless, the presented report shows that severe complications can arise from the procedure. The authors hypothesized that placing an early cerebrospinal shunt would reduce the patient's morbidity before difficulties arose.

Indicators of correct targeting in stereotactic biopsy of intracranial lesions.

Background: Confirmation of whether a stereotactic biopsy was performed in the correct site is usually dependent on the frozen section or on novel tumor-specific markers that are not widely available. Immediate postoperative computed tomography (CT) or magnetic resonance (MR) is routinely performed in our service after biopsy. In this retrospective study, we have carefully analyzed these images in an attempt to determine the presence of markers that indicate appropriate targeting. Methods: Medical records and neuroimages of patients who underwent stereotactic biopsy of intracranial lesions were reviewed. The following variables were assessed: age, sex, anatomopathology, lesion site, complications, diagnostic accuracy, and the presence of image markers. Results: Twenty-nine patients were included in this case series. About 96.6% of the biopsies were accurate according to the permanent section. Of the 86.2% of patients with intralesional pneumocephalus on the postoperative images, 51.7% additionally presented petechial hemorrhage. In 13.8% of the cases, no image markers were identified. Conclusion: This is the first report of intralesional pneumocephalus and petechial hemorrhage as indicators of appropriate targeting in stereotactic biopsy. In the majority of the cases, an immediate postoperative head CT, which is widely available, can estimate how adequate the targeting is. To use intralesional pneumocephalus/ petechial hemorrhages as not only postoperative but also as intraoperative markers of appropriate targeting, it is advised that the surgical wound should be temporarily closed and dressed after the biopsy so that the patient can undergo a CT/MR scan and be checked for the presence of theses markers before removing the stereotactic frame.

The impact of subcaudate tractotomy on delusions and hallucinations in psychotic patients.

BACKGROUND: Delusions and hallucinations, hallmarks of the psychotic disorders, usually do not respond to surgical intervention. For many years, the surgical technique of choice for the treatment of refractory aggressiveness in psychotic patients in our Service was amygdalotomy in isolation or associated with anterior cingulotomy. No improvement of hallucinations and delusions was noticed in any of these patients. To improve the control of aggression, subcaudate tractotomy was added to the previous surgical protocol. The main goal of the present study was to investigate the impact of this modified surgical approach on delusions and hallucinations. METHODS: Retrospective analysis of the medical records of psychotic patients presenting with treatment-resistant aggressiveness, delusions, and hallucinations submitted to bilateral subcaudate tractotomy + bilateral anterior cingulotomy + bilateral amygdalotomy in our institution. RESULTS: Five patients, all males, with ages ranging from 25 to 65 years, followed up by a mean of 45.6 months (17-72 months), fulfilled the inclusion criteria. Delusions and hallucinations were abolished in four of them. CONCLUSION: These results suggest that the key element for relieving these symptoms was the subcaudate tractotomy and that the orbitofrontal and ventromedial prefrontal cortices play an important role in the genesis of hallucinatory and delusional symptoms of schizophrenia and other psychoses.

Tectocerebellar dysraphia and occipital encephalocele associated with trisomy X: case report and review of the literature.

INTRODUCTION: Tectocerebellar dysraphia (TCD) is a rare sporadic malformation associated with severe neurodevelopmental morbidity and high infant mortality. The presence of other ciliopathies worsens the prognosis. Joubert syndrome (JS) is a ciliopathy associated with gene mutations, consisting of midbrain and cerebellum malformations, markedly lack fiber decussation at the level of the pontomesencephalic junction. CASE REPORT: We report the case of a child who was born term with occipital encephalocele (OE), diagnosed with TCD and JS spectrum through computed tomography (CT), magnetic resonance (MR), diffuse tensor imaging (DTI), and clinical findings. She had the OE surgically corrected after spontaneous rupture on the second day after delivery. She developed postoperative ventriculitis, meningitis, and hydrocephalus, successfully treated with intravenous antibiotics and cysto-ventriculostomy, cysto-cisternostomy, third ventriculostomy, and choroid plexus coagulation. G-band karyotyping showed 47, XXX, in all analyzed cells (trisomy X). The infant was followed up for 18 months, presenting, so far, a relatively good outcome. CONCLUSION: This is the first case reported in the literature of the association of TCD/OE/JS spectrum (JSS) with trisomy X (XXX).