The transcallosal transchoroidal approach to the diencephalic-mesencephalic junction: how I do it.

BACKGROUND: Different approaches have to be considered for lesions of the diencephalic-mesencephalic junction based on the localization, extension of the lesion, and relationship to the ventricular system. METHOD: We present the case of a young lady who presented with a cavernoma of the junction of midbrain and diencephalon after an episode of hemorrhage. The microsurgical anatomy of the trans-callosal trans-choroidal approach for this lesion is described along with its advantages and limitations. CONCLUSION: The trans-choroidal approach allows adequate access to lesions of the diencephalic-mesencephalic junction that project into the third ventricle.

Neurosurgical relevance of the dissection of the diencephalic white matter tracts using the Klingler technique.

OBJECTIVE: The Klingler fiber dissection technique is a relevant and reliable method for neurosurgery to identify with accuracy the fine structure of the brain anatomy highlighting white matter tracts. In order to demonstrate the significance of the application of this technique, we aimed to observe the course and relations of the mammillothalamic and habenulo-interpeduncular tracts as there are very few papers showing these important diencephalic tracts. MATERIAL AND METHODS: Twelve formalin-fixed brains were dissected using the Klingler technique in order to expose the medial diencephalic surface. Diencephalic white matter tracts, particularly the mammillothalamic and habenulo-interpeduncular tracts, were dissected using wooden spatulas and metallic dissectors with different sizes and tips. Several measurements were performed in both dissected hemispheres relative to the mammillothalamic and habenulo-interpeduncular tracts. RESULTS: The course and length of these two tracts were visualized and the relations with other fiber systems and with the neighboring gray matter structures quantified and registered. The mammillothalamic tract approximately marks the anteroposterior coordinate of the anterior pole of the subthalamic nucleus in the anterior commissure - posterior commissure plane. CONCLUSION: The present study helps to understand the three-dimensional architecture of the white matter systems of tracts when the Klingler technique is used. The numerical data obtained may be helpful to neurosurgeons while approaching brain paraventricular and ventricular lesions and deep brain stimulation. Finally, the anatomical knowledge can lower surgical complications and improve patient care particularly in the field of neurosurgery.

Oligodendrocyte precursors originate in the parabasal band of the basal plate in prosomere 1 and migrate into the alar prosencephalon during chick development.

Oligodendrocytes are the myelin-forming cells in the central nervous system of vertebrates. Oligodendrocyte precursors arise from multiple restricted foci distributed along the antero-posterior axis of the developing brain. In chick and mouse embryos, oligodendrocyte precursors of the anterior forebrain emerge from neuroepithelial cells of the subpallium and migrate tangentially to invade the entire telencephalon (Olivier et al. (2001) Development 128:1757-1769). In the diencephalon, oligodendrocyte neuroepithelial precursors seem to be mainly located in the basal plate of caudal prosomeres, but very little is known about their distribution and maturation at later stages of embryonic development. Thus, in this work, we studied the origin and migration of oligodendrocyte precursos in the diencephalon of quail-chick chimeras. Homotopic and homochronic grafts demonstrated that, during embryonic development, diencephalic oligodendrocytes emerge from a common neuroepithelial domain in the basal plate of prosomere 1 and migrate tangentially, invading the dorsal regions of the diencephalic prosomeres and the telencephalon.

The perforating branches of the P1 segment of the posterior cerebral artery.

The perforating branches of the P1 segment of the posterior cerebral artery are vulnerable to injury. Because of their close proximity to the basilar artery, the vulnerability occurs especially during surgical interventions for vascular pathologies such as basilar apex aneurysms. Therefore, extensive knowledge of the microsurgical anatomy of this area is mandatory to prevent poor post-operative outcomes. We microscopically examined 28 P1 segments obtained from 14 adult fresh cadaver brains (6 silicone injected, 8 freshly examined). The P1 segments ranged between 2.8mm and 12.2mm (mean 6.8mm) in length with a mean outer diameter of 1.85 mm (range 0.8-4.5mm). All 94 thalamoperforating branches identified in 27 P1 segments (mean 3.35 branches per segment) arose from the postero-superior aspect of P1 and were the most proximally originating branch in nearly all specimens (96.4%). In addition in 28 P1s, 12 short circumflex arteries (42.8%; mean 0.42 branches per segment), 16 long circumflex arteries (57.1%; mean 0.57 branches per segment) and 10 medial posterior choroidal arteries (35.7%; mean 0.35 branches per segment) were identified and all originated from the posterior or postero-inferior surface of the P1 segment. When the P1 segment had more than one type of branch, it was the short circumflex arteries that were always more proximal in origin than the others. The medial posterior choroidal arteries were always more distal in origin. All three branches were not observed together in any of the P1 segments. The findings in this, and future, anatomical studies may help to reduce the post-surgical morbidity and mortality rates after surgery for posterior circulation aneurysms.

Transtemporal-transchoroidal approach and its transamygdala extension to the posterior chiasmatic cistern and diencephalo-mesencephalic lesions.

The aim of this report is to illustrate the successful surgical management of five patients with suprasellar retrochiasmatic and diencephalo-mesencephalic tumours, using a trans-amygdala extension of the trans-temporal/trans-choroidal fissure approach. The procedure is described for five surgically treated patients with such lesions that includes three retrochiasmatic craniopharyngiomas, one hypothalamic hamartoma, and one pilocytic astrocytoma in the left crus cerebri. The management procedure included computed tomography scan (CT scan) and magnetic resonance imaging (MRI). The trans-temporal/trans-choroidal fissure approach enabled us to perform total tumour resection in four patients and a subtotal resection in one. Some technical aspects and pitfalls of the procedure are discussed. This method creates optimum conditions for a radical excision of various suprasellar retrochiasmatic and diencephalo-mesencephalic tumours without mortality and only minimum morbidity. However, no single surgical approach can provide access to the entire variety of tumours located in the suprasellar retrochiasmatic and diencephalo-mesencepalic region. Surgical approaches must be tailored to the site, type of lesion, and its extensions. This method is only another surgical option. Its successful use requires a familiarity with the anatomy of these regions and an understanding of its specificity for a radical excision of some selected tumours, as well as its limitations to access others types of lesions. Although, it seems effective, this approach needs to be evaluated by further experience, owing to the small number of patients reported in this series.

Deep brain stimulation in intraoperative MRI environment - comparison of imaging techniques and electrode fixation methods.

We performed 118 consecutive DBS cases from November 1999 to June 2002. Intraoperatively there were 10 cases studied with fluoroscopy, 73 with 0.2 Tesla (T) MRI and 35 with 1.5 T MRI. Ten electrodes were secured by Medtronic caps, 25 by methyl methacrylate with titanium miniplates, and 82 by Navigus caps. The 3-dimensional displacement between the planned target and actual electrode position (3DD) was determined by fusing the postoperative MRI with the preoperative imaging. The 3DD for using Medtronic caps, methyl methacrylate with miniplates, and Navigus caps were 4.80 +/- 3.16, 2.64 +/- 1.26 and 2.23 +/- 1.15 mm (mean +/- SD), respectively. Navigus caps had statistically significant accuracy (P = 0.03) in holding the electrode when compared with Medtronic caps, and it facilitated electrode revision. The fixation devices significantly affect the final vertical position of the electrode. The 3DD for fluoroscopy, 0.2 T and 1.5 T MRI cases were 4.80 +/- 3.16, 2.31 +/- 1.21 and 2.34 +/- 1.14 mm (mean +/- SD), respectively. No statistically significant difference (P = 0.91) in 3DD was demonstrated between 0.2 T and 1.5 T MRI cases. The presence of intraoperative 1.5 T MRI allowed near real-time electrode position confirmation and early detection of hemorrhagic complications. Satisfactory microelectrode recording was feasible in low-field 0.2 T and high-field 1.5 T MRI environments. Further studies on performing DBS in real-time intraoperative MRI are warranted.

How long should patients refrain from oral food and fluid intake after general anaesthesia? An assessment of the swallowing reflex of postoperative neurosurgical patients.

OBJECTIVE: Our aim was to detect swallowing abnormalities in patients after short-term neurosurgical interventions under general anaesthesia, comparing patients with supratentorial operations with a group undergoing extracranial neurosurgery (nucleotomy). METHODS: 20 patients in each group were examined by fiberoptic endoscopic evaluation of swallowing (FEES) after general anaesthesia. RESULTS: No patient demonstrated dysphagia, aspiration, or oxygen desaturation. CONCLUSION: In these patient groups, early postoperative feeding was safe. Postoperative food intake can probably be allowed early after general anaesthesia.

[Water electrolyte disorders in the postoperative clinical picture of basal-diencephalitic tumors]. / Vodno-élektrolitnye narusheniia v klinike posleoperatsionnogo perioda pri opukholiakh bazal'no-diéntsefal'noí lokalizatsii.

The paper deals with the relationship of homeostatic and motivational disorders in the postoperative clinical picture in basal-diencephalic tumors. The material included 354 clinical observations of: hypophysial adenoma (n = 135); craniopharyngioma (n = 71); tumors of the third ventricle (n = 88); basal meningiomas (n = 60). A comparative analysis of the findings allowed the authors to support that there are typical variants of changes in the patients' status, which reflect the nature of ion-osmotic disorders. The most significant mental disorders were transient hyperosmolar-hypernatriemic disturbances. The poor predictors were persistent hypernatriemia concurrent with evolving coma, systemic hemodynamic and respiratory disorders. Hyponatriemia is a better predictor of ionosmotic disorders, which requires a careful postoperative monitoring and a comparison of its findings with the specific features of intensive care performed.

Role of the pons in hypoxic respiratory depression in the neonatal rat.

The main purpose of this study was to evaluate the role of the pons in hypoxic respiratory depression (HRD) of the neonatal rat. Experiments were conducted using the isolated brainstem-spinal cord preparation of the neonatal rat (1-3 days old). The brainstem was transected at various levels. We found that ablation of the diencephalon decreased respiratory frequency (fR), and conversely, that ablation of the midbrain or pons increased fR. In the preparation with the pons intact (without the midbrain), hypoxia (superfusate PO2 = 56 mmHg) caused strong depression of respiratory activity, which was characterized by a steady decrease in fR and in integrated inspiratory burst amplitude (integral of Phr). In the preparation with the intact ventral pons (without midbrain and dorsal pons) we observed similar, though weaker, HRD. When the entire pons was ablated, integral of Phr was little depressed by hypoxia and thus, HRD was further attenuated. We conclude that the pons contributes importantly to the induction of hypoxic respiratory depression in the neonatal rat. Both the ventral and dorsal portions of the pons are involved in the control of hypoxic respiratory depression. In addition, we show that the respiratory modulatory functions of the diencephalon (facilitating) and midbrain (inhibitory) are already expressed at the time of birth.

D1 dopamine receptor stimulation inhibits firing activity of midbrain dopamine neurons in reserpine treated rats: an effect eliminated after hemitransection of diencephalon.

It has been reported that systemic administration of the D1 dopamine (DA) receptor agonist SKF 38393 inhibits the firing rate of substantia nigra pars compacta (SNC, A9) DA neurons after repeated reserpine treatment in locally anesthetized rats, although SKF 38393 induces little effect on the firing of midbrain DA neurons in normal rats. The present study found that local pressure microejection of SKF 38393 (10(-2) M, 20-100 nl) to SNC or substantia nigra pars reticulata (SNR) failed to influence the firing of SNC DA neurons in reserpinized rats (reserpine 1 mg/kg x 6 days, s.c.); subsequent intravenous (i.v.) injection of SKF 38393 (4 mg/kg), however, inhibited their firing and the inhibition was reversed by the D1 receptor antagonist SCH 23390. Similarly, systemic administration of SKF 38393 (4 mg/kg, i.v.) inhibited the firing of ventral tegmental area (VTA, A10) DA cells in reserpinized rats, while local microejection of SKF 38393 (10(-2) M, 30-60 nl) did not affect their firing. Furthermore, the inhibitory effect of systemic SKF 38393 on firing rate of either SNC or VTA DA neurons in reserpinized rats was eliminated after hemitransection of diencephalon. These results suggest that repeated reserpine treatment renders midbrain DA neurons responsive to D1 receptor stimulation and that D1 receptor agonist-induced inhibition of midbrain DA cell firing in reserpinized rats may require the involvement of long-loop feedback pathways.

Functional stereotactic surgery for hemiballism.

The symptomatic and functional outcomes of a series of 14 patients with disabling and medically refractory hemiballism who were treated with functional stereotactic surgery are reported. Seven (50%) of the 14 patients had concomitant hemichorea. To relieve the hyperkinesia, the 14 patients underwent a total of 15 stereotactic operations (one patient had a second stereotactic procedure). Combined lesions in the contralateral zona incerta and the base of the ventrolateral (oroventral) thalamus were applied in 13 instances. The zona incerta was reached by means of a movable chord electrode to obviate the need for repeated puncture. In two instances the medial pallidum was used as the stereotactic target. Hemiballism was abolished or considerably improved in 13 (93%) of 14 patients in the immediate postoperative phase. Residual dyskinesia was evaluated using the hemiballism/hemichorea outcome rating scale. Long-term follow-up review was available for 13 of the 14 patients (mean follow-up period 11 years). Persistent improvement in the hemiballism was found in 12 of these 13 patients: seven patients (54%) were free of any hyperkinesia and five patients (39%) had minor residual and predominantly hemichoreic hyperkinesia. One of the 13 patients presented with a probable psychogenic movement disorder at long-term follow-up examination. Persistent morbidity, most likely related to the operative intervention, was detected in three of the 13 patients; this included mild hemiparesis and dystonia. Functional disability was assessed using the Huntington's Disease Activities of Daily Living scale. The patients' preoperative mean value of 83% of maximum disability was reduced to a mean of 30% observed at long-term follow-up review (p < 0.001). The residual disability exhibited in most older patients was associated with cardiovascular disease. The authors compare their findings with the results of 44 cases reported previously. The authors contend that functional stereotactic surgery should be considered in patients with persistent, medically refractory hemiballism.

An experimental study to evaluate the accuracy of diencephalic and pallidal target localization using the Brown-Roberts-Wells stereotactic system and unreformatted axial GE8800 CT scanning.

An experimental study was undertaken to evaluate the accuracy with which the intercommissural line (IL) length and anterior-posterior commissural (AC-PC) plane could be selected using unreformatted axial CT8800 imaging. Using these reference points, the Schaltenbrandt and Bailey stereotactic atlas and the Brown-Roberts-Wells (BRW) stereotactic system 1.82 mm ball bearings were deposited at selected diencephalic and pallidal targets in cadaver brains. There were errors in both IL length (median 1.5 mm) and AC-PC plane (median forward angulation of 9 degrees) estimation. Ball bearing deposition into large nuclei such as the pulvinar and globus pallidus and those in proximity to the mid IL such as the nuclei ventro oralis anterior (Voa), ventro oralis posterior (Vop) and ventro intermedius (Vim) was generally good; however, localization of the relatively small intralaminar nucleus was poor. This study suggests that when the AC and PC are not well imaged on sagittal reformations of axial diencephalic CT scans estimation of the AC-PC plane and IL from axial CT scans may be accurate enough for anatomical localization of certain functional stereotactic targets. The implications of this experimental study to operative functional stereotaxy are discussed.

Radiosurgical treatment of gliomas of the diencephalon.

The results of Leksell Gamma Knife treatment of diencephalic gliomas are presented. Eight tumours in seven patients form the basis of this report. 7 patients, 4 males and 3 females. The age range was 7.5 to 33 years with a mean of 18 years. Mean follow-up was 21 +/- 12 months. In 4 patients the tumour had been reduced in volume by an open internal decompression procedure. The location of the tumour will determine the risks of treatment. With anterior lesions there is risk of endocrinological and visual pathway damage. With a pineal region lesion there is a risk of diplopia. In this series no tumour has increased in volume. Four have decreased and one has disappeared. Two patients suffered temporary diplopia. No visual disturbance has been observed to date. No hypothalamic disturbance has been observed yet. These tumours are dangerous not so much because of their biological nature as because of their location. However, the biological nature of the tumours, with the close concordance between the radiological and actual extent make them appropriate targets for radiosurgery as a primary treatment. The present study gives preliminary support to this line of treatment.

Accuracy of ventrolateral thalamic nucleus localization using unreformatted CT scans and the B-R-W system. Experimental studies and clinical findings during functional neurosurgery.

The accuracy with which the ventrolateral thalamic nucleus could be targetted using the BRW stereotactic system and unreformatted axial CT imaging was evaluated in cadaver brains mounted in a skull. Ball bearings (1.82 mm diameter) were placed in the nuclei ventro intermedius (Vim), ventro oralis anterior (Voa) and posterior (Vop) and the brains then sectioned, the locations of the ball bearings relative to the anterior (AC) and posterior commissures (PC) measured and evaluated with reference to a Schaltenbrandt and Bailey stereotactic atlas. Targetting of the ventrolateral thalamic region was frequently accurate (77%) but because of errors in estimation of the AC-PC plane (mean forward angulation of 9 degrees) some ball bearings were placed too deeply in the Fields of and Forel, zona incerta and rostral subthalamic nucleus. Ventrolateral thalamotomy using the BRW stereotactic system and unreformatted axial CT imaging was undertaken in six patients with tremor due to a range of pathologies. The tremor was abolished or altered in four patients whilst no lesion was made in the other two patients since no site that reduced the tremor, could be located. The surgical and clinical implications of this study are discussed.

Translingual approach of the basal surface of the diencephalon of the rat and retrograde labeling from the median eminence.

A unique surgical procedure is described by which the basal surface of the diencephalon can be exposed without cannulation of the trachea. The basal surface of the diencephalon is exposed through a midsagittal incision by splitting the oral diaphragm, tongue, and soft palate respectively. Then a small hole is drilled in the base of the skull. After manipulation on the base of the brain is completed, the hole in the skull is plugged with Histoacryl and the soft palate and tongue are sutured. Rats having such interventions survive in excellent condition for days without the need of intensive medical care.

Long-term results of stereotaxy in the treatment of essential tremor.

In patients with severe tremor that is resistant to drug therapy, stereotactic coagulation can achieve a satisfactory and lasting reduction of the movement disorders. Very few long-term studies have been conducted following stereotactic operations. From 1964 to 1984, 104 patients with a diagnosis of essential tremor were operated on in the Division of Stereotaxy and Neuronuclear Medicine. After an average follow-up period of 8.6 years, 65 patients were examined. In 80%, the success of the stereotactic operation was still evident. Complete disappearance or substantial reduction of the tremor was determined in 69% and moderate improvement in 11.9% of the patients.