Transcallosal-Transchoroidal Fissure Approach for Midbrain and Thalamic Cavernous Malformations: 2-Dimensional Operative Video.

INDICATIONS CORRIDOR AND LIMITS OF EXPOSURE: Cavernous malformations of the third ventricle arise from the medial thalamus and/or periaqueductal midbrain. Microsurgical resection is indicated when the lifetime risk of hemorrhage outweighs the surgical risks. ANATOMIC ESSENTIALS NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: superior sagittal sinus, callosomarginal and pericallosal arteries, corpus callosum, foramen of Monro, choroidal fissure, fornix, thalamostriate veins, internal cerebral veins (ICVs), velum interpositum, and thalamus. ESSENTIAL STEPS OF THE PROCEDURE: The patient consents to the procedure. With the patient supine, the head is turned 90° and laterally flexed 45°. A bifrontal craniotomy positioned two-thirds anterior and one-third posterior to the coronal suture is performed. The interhemispheric fissure is opened, and a 2-cm corpus callosotomy is performed. Choroid plexus cauterization exposes the choroidal fissure. Sharp division of the taenia fornicea opens the velum interpositum, where the thalamostriate vein can be followed around the venous angle to the ICV. The anterior septal vein may be divided to communicate between the foramen of Monro and choroidal fissure. Dissection between the ICVs opens the velum interpositum into the third ventricle. PITFALLS/AVOIDANCE OF COMPLICATIONS: Frontal or deep vein occlusion causes venous infarction, and dissection on the nondominant hemisphere is preferred. Other complications include arterial infarction, fornix injury from choroidal fissure dissection or forniceal retraction, and thalamic or midbrain injury during lesion resection. VARIANTS AND INDICATIONS FOR THEIR USE: The contralateral choroidal fissure is used for low-lying medial thalamic and midbrain lesions. The ipsilateral choroidal fissure is used for high-lying or large lesions extending laterally. Transchoroidal approaches are not needed for superior (transcallosal only) or anterior (contralateral transcallosal-contralateral transforaminal) thalamic lesions. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Trans-lamina terminalis suprategmental approach for ventral midbrain lesions: Technical note.

Surgical resection of lesions located in the ventral midbrain is challenging. Few approaches and safe entry zones (SEZs) have been proposed and used to remove this type of lesion, and each has its limitations. Using two illustrating cases, the authors describe a trans-lamina terminalis suprategmental approach for removing ventral midbrain lesions. This approach provides a straight surgical trajectory with sparse neurovascular structures and can be performed with a standard pterional or subfrontal craniotomy. It may be the ideal approach for ventromedial midbrain lesions extending towards the third ventricle.

The interpeduncular fossa approach for resection of ventromedial midbrain lesions.

The authors describe the interpeduncular fossa safe entry zone as a route for resection of ventromedial midbrain lesions. To illustrate the utility of this novel safe entry zone, the authors provide clinical data from 2 patients who underwent contralateral orbitozygomatic transinterpeduncular fossa approaches to deep cavernous malformations located medial to the oculomotor nerve (cranial nerve [CN] III). These cases are supplemented by anatomical information from 6 formalin-fixed adult human brainstems and 4 silicone-injected adult human cadaveric heads on which the fiber dissection technique was used. The interpeduncular fossa may be incised to resect anteriorly located lesions that are medial to the oculomotor nerve and can serve as an alternative to the anterior mesencephalic safe entry zone (i.e., perioculomotor safe entry zone) for resection of ventromedial midbrain lesions. The interpeduncular fossa safe entry zone is best approached using a modified orbitozygomatic craniotomy and uses the space between the mammillary bodies and the top of the basilar artery to gain access to ventromedial lesions located in the ventral mesencephalon and medial to the oculomotor nerve.

Giant cavernous malformation in the ventrolateral midbrain with extension into the thalamus: a case report of a paramedian supracerebellar transtentorial approach.

Cavernous malformations (CMs) of the midbrain and thalamus are relatively rare and particularly difficult to be resected given their location in eloquent tissues. Here, we report a case of a 14-year-old boy who experienced repeated and progressive right hemiparesis. Image examinations showed a gradually enlarged CM originated in the left ventrolateral midbrain extending to the left thalamus with repeated hemorrhage. By performing a paramedian supracerebellar transtentorial approach, the CM was totally removed, and the patient recovered without any new neurological deficit. The authors' experience suggests that this approach is eminent in treating giant lesions involving the ventrolateral midbrain and thalamus.

Holmes tremor: Clinical description, lesion localization, and treatment in a series of 29 cases.

OBJECTIVE: To describe the clinical features, etiology, findings from neuroimaging, and treatment results in a series of 29 patients with Holmes tremor (HT). METHODS: A retrospective study was performed based on review of medical records and videos of patients with HT diagnosis. RESULTS: A total of 16 women and 13 men were included. The mean age at the moment of CNS insult was 33.9 ± 20.1 years (range 8-76 years). The most common causes were vascular (48.3%), ischemic, or hemorrhagic. Traumatic brain injury only represented 17.24%; other causes represented 34.5%. The median latency from lesion to tremor onset was 2 months (range 7 days-228 months). The most common symptoms/signs associated with HT were hemiparesis (62%), ataxia (51.7%), hypoesthesia (27.58%), dystonia (24.1%), cranial nerve involvement (24.1%), and dysarthria (24.1%). Other symptoms/signs were vertical gaze disorders (6.8%), bradykinesia/rigidity (6.8%), myoclonus (3.4%), and seizures (3.4%). Most of the patients had lesions involving more than one area. MRI showed lesions in thalamus or midbrain or cerebellum in 82.7% of the patients. Levodopa treatment was effective in 13 out of 24 treated patients (54.16%) and in 3 patients unilateral thalamotomy provided excellent results. CONCLUSIONS: The most common causes of HT in our series were vascular lesions. The most common lesion topography was mesencephalic, thalamic, or both. Treatment with levodopa and thalamic stereotactic lesional surgery seems to be effective.

Intracranial ablative procedures for the treatment of chronic pain.

Three main techniques delineate a possible role for intracranial ablative procedures in patients with chronic pain. Recent studies demonstrate a continued need for clinical investigation into central mechanisms of neuroablation to best define its role in the care of patients with otherwise intractable and severe pain syndromes. Cingulotomy can result in long-term pain relief. Although it can be associated with subtle impairments of attention, there is little risk to other cognitive domains.

[Temporal transchoroidal approach for tumors of the midbrain and thalamus].

Surgical approach to the tumors of deep localization depends on the predominant direction of tumor growth. The main task of the surgeon in such cases is to choose less traumatic approach with a sufficient angle of operational action to achieve greater surgical radicality. The article describes temporal transchoroidal approach to the tumors of the midbrain, thalamus, and optic tract. This approach in selected cases allows to remove deep-seated tumors with less damage compared with pterional and subtemporal approach.

Intestinal fatty acid infusion modulates food preference as well as calorie intake via the vagal nerve and midbrain-hypothalamic neural pathways in rats.

The intestine plays important roles in the regulation of feeding behavior by sensing macronutrients. Intestinal fatty acids strongly suppress food intake, but little is known about whether intestinal fatty acids affect food preference. We investigated the effects of jejunal fatty acids infusion on food preference by conducting two-diet choice experiments in rats fed a high-fat diet (HFD) and a high-carbohydrate diet (HCD). Jejunal linoleic acid (18:2) infusion reduced HFD intake dose-dependently, while HCD intake increased with the middle dose of the infusion we examined (100 µL/h) and reduced to the control level with the higher doses (150 and 200 µL/h). α-Linolenic acid (18:3), but not caprylic acid (8:0), altered the food preference and total calorie intake in the same manner as linoleic acid. Linoleic acid infusion dose-dependently increased plasma glucagon-like peptide-1, peptide YY and cholecystokinin levels, but not ghrelin levels. Subdiaphragmatic vagotomy or midbrain transection prevented the change in food preference and total calorie intake by linoleic acid infusion. Jejunal linoleic acid infusion increased norepinephrine turnover in the paraventricular hypothalamic nucleus, while intracerebroventricular injection of idazoxan, an α2-adrenergic receptor (AR) antagonist, suppressed the increased HCD intake, but did not affect the decreased HFD intake. These findings indicated that intestinal long-chain fatty acids modulated food preference as well as total calorie intake via the vagal nerve and midbrain-hypothalamic neural pathways. The effects of the α2-AR antagonist in the brain suggested that the brain distinctly controlled HCD and HFD intake in response to jejunal linoleic acid infusion.

Supracerebellar-supratrochlear and infratentorial-infratrochlear approaches: gravity-dependent variations of the lateral approach over the cerebellum.

OBJECTIVE: Lateral supracerebellar-infratentorial approaches are established for lesions in ambient cistern and posterolateral midbrain, but published surgical experiences do not describe results with this approach in the sitting position. Gravity retraction of the cerebellum opens this surgical corridor and dramatically alters exposure, creating 2 variations of the lateral supracerebellar-infratentorial approach: the supracerebellar-supratrochlear approach and the infratentorial-infratrochlear approach. METHODS: We reviewed our experience treating cavernous malformations and arteriovenous malformations (AVMs) of the posteroinferior thalamus and posterolateral midbrain by use of supracerebellar-supratrochlear and infratentorial-infratrochlear approaches. Microsurgical technique, clinical data, radiographic features, and neurological outcomes were evaluated. RESULTS: During an 11-year surgical experience with 341 cavernous malformation patients and 402 AVM patients, 8 patients were identified, 6 with cavernous malformations and 2 with AVMs. Infratentorial-infratrochlear approaches were used in 4 patients (50%), including 3 with inferolateral midbrain cavernous malformations. Supracerebellar-supratrochlear approaches were used in 4 patients (50%), including 2 with posterior thalamic lesions surfacing on pulvinar. Resections were radiographically complete in all cases. There were no new, permanent neurological deficits, nor were there any medical or surgical complications. There has been no evidence of rebleeding or recurrence. CONCLUSIONS: Gravity retraction of the cerebellum transforms the lateral supracerebellar-infratentorial approach, enhancing exposure and approach trajectories that can be achieved with patients in prone or lateral positions. The increased upward viewing angle of the supracerebellar-supratrochlear approach accesses the posteroinferior thalamus. The increased downward-viewing angle of the infratentorial-infratrochlear approach accesses cerebellomesencephalic fissure and posterolateral midbrain. These approaches open wide corridors for safe surgical resection of symptomatic cavernous malformations and AVMs.

An anatomical assessment of the supracerebellar midline and paramedian approaches to the inferior colliculus for auditory midbrain implants using a neuronavigation model on cadaveric specimens.

The inferior colliculus (IC) is an alternative site for electrode placement in neural deafness due to its surgical accessibility and its well-known tonotopic stratification. In patients where tumor surgery has already occurred and the cerebellopontine angle contains scar tissue or tumor-remnants, midline and paramedian supracerebellar approaches are alternative routes. They are often avoided due to concerns regarding the venous drainage of the cerebellum, the electrode trajectory and the course of the electrode cable. We studied these surgical routes in five neuronavigated fixed cadaveric specimens. For paramedian and midline approaches, the transverse sinus was exposed 5.8mm on average. A mean of 1.6 cerebellar veins, with an average diameter of 2.0mm, draining to the tentorium were transected to reach the tentorial notch. Only 0.4 arterial branches were met. We conclude that the supracerebellar midline and paramedian approaches provide a good exposure of the IC and offer safe and viable alternative routes to the IC. Additionally, they provide a wider angle of action for optimal electrode placement.

Mesencephalic ependymal cysts: treatment under pure endoscopic or endoscope-assisted keyhole conditions.

OBJECT: Primary intracranial ependymal cysts are extremely rare. Similar to congenital intraparenchymal cysts in the mesencephalon they usually occur with symptoms of an occlusive hydrocephalus or symptoms like Parinaud syndrome, dizziness, or gait disturbance. The objective of this study was to evaluate the surgical methods for the treatment of these cysts and the clinical outcome of the patients. METHODS: The authors present the clinical records of 8 patients who were treated in their department for symptomatic mesencephalic ependymal cysts in the past 10 years. The patient age ranged from 22 to 60 years with a mean age of 44 years. In 4 cases the authors performed a suboccipital infratentorial supracerebellar approach by using endoscope-assisted microsurgery. The other 4 patients underwent a pure endoscopic procedure over a frontal bur hole trepanation. RESULTS: Four patients became symptom free, and the remaining 4 improved significantly after a mean follow-up duration of 38.5 months (range 5-119 months). One patient underwent 2 operations: first a ventriculocystostomy and 4 months later endoscopic third ventriculostomy because of recurrent hydrocephalus. In 1 case a second surgery was necessary because of a wound infection. In all of the patients an adequate fenestration of the cyst was achieved. CONCLUSIONS: A symptomatic mesencephalic ependymal cyst is an indication for neurosurgical intervention. These cysts can be treated successfully and most likely definitively by a pure endoscopic or endoscope-assisted keyhole neurosurgical technique. There were no morbid conditions or death due to the procedures in this group of 8 patients. Therefore, the authors regard these surgical procedures to be good alternatives to treatments such as shunt placement or stereotactic aspiration of the cysts.

Transanterior perforating substance approach to the thalamomesencephalic junction.

OBJECTIVE: Lesions in the thalamomesencephalic junction can be reached via an anterolateral approach, interhemispheric approach, transcortical (parieto-occipital lobule) approach, subtemporal approach, supracerebellar approaches, or transsylvian-insular approach. We now describe a new approach, a transanterior perforating substance approach, to this territory. METHODS: A 33-year-old man with progressive right arm tremors, mild hemiparesis, and a cavernous malformation of the thalamomesencephalic junction was followed for 5 years. Because of clinical progression, he underwent a left orbitozygomatic approach to the cavernous malformation, which could not be accessed because of a high-riding basilar artery. Hence, a new transsylvian corridor of exposure was developed using frameless neuronavigation. The trajectory, which was dorsal to M1, led through the perforating branches of M1. Care was taken to avoid violating any arterial perforators. To reach the lesion, a small opening into the brain was created near the optic tract. RESULTS: The cavernous malformation was resected totally. Postoperatively, the patient's tremors were cured. No visual deficits were encountered. Imaging showed a small ischemic stroke in the basal ganglia likely related to manipulation of a perforator. Initially, his hemiparesis worsened, but it improved significantly within 10 months with only a moderate decrease in strength. CONCLUSION: The transanterior perforating substance approach effectively allowed access to the thalamomesencephalic junction and was associated with significant morbidity. However, the safety of the approach needs further validation. Neuronavigation is indicated to choose the most direct trajectory through the M1 perforators. Tractography may help protect the optic tract.

Thalamomesencephalic ossified cavernoma presenting with Holmes' tremor.

BACKGROUND: Midbrain cavernoma associated with Holmes' tremor is a rare entity. Although there have been 4 other cases of Holmes' tremor caused by a cavernoma, this is the first case that was cured by surgical removal of the cavernoma. In addition, heavy ossification and Holmes tremor as a clinical presentation are 2 unusual features of the cavernoma. Possible mechanisms of these very rare entities are discussed in relation to the present report and relevant literature is reviewed. CASE DESCRIPTION: We present a case of 60-year-old woman with heavily ossified cavernoma of the thalamomesencephalic junction with neuroimaging and histologic features. The only manifestation was Holmes' tremor. The patient was operated on via posterior interhemispheric approach while in the sitting position. After the arachnoid folds of the quadrigeminal cistern were opened, the thin neural tissue on the surface of the dorsal midbrain was incised and the lesion was visualized and totally removed as a single piece. The tremor was almost completely suppressed. CONCLUSION: Ossified cavernoma is a rare entity but has a characteristic MRI appearance. It should be considered in the differential diagnosis of intracerebral hypointense lesions on both T1- and T2-weighted MR images because they are potentially curable by surgical removal.

Ablative procedures for chronic pain.

The advent of neuroaugmentative techniques has reduced the application of neuroablative procedures, especially as regards pain of functional origin. Although intracranial ablative procedures are now rarely performed, spinal ablative procedures, such as anterolateral cordotomies or midline myelotomies, remain important in the management of cancer pain. These procedures produce immediate and satisfactory pain relief with acceptable complication rates. An important future trend will be the application of radiosurgery guided by functional imaging (eg,fMRI, PET) to place such intracranial lesions as cingulotomies or medial thalamotomies.

Surgical considerations regarding giant dilations of the perivascular spaces.

OBJECT: Dilations of brain perivascular spaces (PVSs), also known as Virchow-Robin spaces, are routinely identified on magnetic resonance imaging studies of the brain and recognized as benign normal variants. Giant dilations occur only rarely and can be easily misdiagnosed as central nervous system tumors. The relevant surgical literature was reviewed to help establish indications for surgical intervention in these typically benign lesions. METHODS: Giant dilations of the PVSs in 12 patients who had undergone surgery for several different indications were identified. Both clinical and radiographic presentations of these patients were reviewed along with the surgical procedures. CONCLUSIONS: Dilations of the PVSs can become giant lesions that may necessitate surgical intervention to relieve mass effect or hydrocephalus. The relationship of these lesions to neurological symptoms such as tremor and seizures remains unclear.

Thalamic deep brain stimulation for disabling tremor after excision of a midbrain cavernous angioma. Case report.

Thalamic deep brain stimulation (DBS) has been demonstrated to be effective for the treatment of parkinsonian or essential tremor. To date, however, few data exist to support the application of this method to treat midbrain tremor. A 24-year-old right-handed man underwent radiosurgery and subsequent resection of a recurrently hemorrhaging cavernous angioma located in the left side of the midbrain. The surgery exacerbated severe choreoathetotic resting and action tremors of his right extremities and trunk. The patient underwent placement of a deep brain stimulator into the left ventral intermediate nucleus of the thalamus (Vim). Postoperatively, decreased truncal ataxia and right-sided choreoathetotic tremor were demonstrated, with a 57% increase in dexterity as measured by task testing. The authors demonstrate that DBS can be an effective treatment modality for disabling tremor after resection of a midbrain cavernous angioma.

[Neurophysiological monitoring in the treatment of pain]. / Monitorización neurofisiológica en la terapia del dolor.

INTRODUCTION: The concept of transynaptic deafferentation secondary to a lesion is the basis of the therapeutic criteria of functional neurosurgery. DEVELOPMENT: Pain due to deafferentation requires clinical neurophysiological techniques for characterization, and when appropriate, for localization of the level of the lesion and the ectopic focus or foci which cause the pain syndrome. However, monitoring therapeutic interventions in the pain clinic is an ever increasing need, and obliges the clinical neurophysiologist to master the range of techniques involved in his specialty, so that he can use the most suitable techniques and methods as required by each condition and/or case. The use of techniques such as micro-recordings of the unitary or multiunitary activity of the nerves or nuclei, intracerebral evoked potentials, nociceptive evoked potentials, reflexology, polysomnography and topography, together with techniques such as percutaneous objective localization of deep nerves, allows quantitative evaluation pre-, intra- and postoperative. CONCLUSION: The development of neuromodulation, and in particular of acute or long-term neurostimulation by use of percutaneous techniques, offers an effective therapeutic option in the field of clinical neurophysiology.

Effects of midbrain and spinal cord transections on sympathetic nerve responses to heating.

In the present study, we investigated the contributions of forebrain, brain stem, and spinal neural circuits to heating-induced sympathetic nerve discharge (SND) responses in chloralose-anesthetized rats. Frequency characteristics of renal and splenic SND bursts and the level of activity in these nerves were determined in midbrain-transected (superior colliculus), spinal cord-transected [first cervical vertebra (C1)], and sham-transected (midbrain and spinal cord) rats during progressive increases in colonic temperature (T(c)) from 38 to 41.6-41.7 degrees C. The following observations were made. 1) Significant increases in renal and splenic SND were observed during hyperthermia in midbrain-transected, sham midbrain-transected, C1-transected, and sham C1-transected rats. 2) Heating changed the discharge pattern of renal and splenic SND bursts and was associated with prominent coupling between renal-splenic discharge bursts in midbrain-transected, sham midbrain-transected, and sham C1-transected rats. 3) The pattern of renal and splenic SND bursts remained unchanged from posttransection recovery levels during heating in C1-transected rats. We conclude that an intact forebrain is not required for the full expression of SND responses to increased T(c) and that spinal neural systems, in the absence of supraspinal circuits, are unable to markedly alter the frequency characteristics of SND in response to acute heat stress.

Brain targets for pain control.

A variety of brain sites have been targeted for surgical treatment of intractable pain. Both ablative and chronic stimulation procedures have been reported to attenuate such pain. These targets include the thalamus and its projections, the periventricular gray, the cingulate cortex and the motor cortex. An overview of these procedures and their efficacy is provided.