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.

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.

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.

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.

Ascending afferents to the telencephalon of ranid frogs: an anterograde degeneration study.

Sources of telencephalic afferents were examined in two species of frogs, Rana catesbeiana and Rana pipiens, by study of anterograde degeneration resulting from hemisection of the brain at the isthmus or at the caudal border of the thalamus and from electrolytic lesions in various portions of the diencephalon. The results indicate that some telencephalic afferents arise from levels caudal to the isthmus, that some striatal afferents arise from a level between the isthmus and the caudal border of the thalamus, and that a projection to the ipsilateral striatum arises from the anterior and/or middle portions of the dorsal thalamus. Diencephalic projections to pallial portions of the hemisphere were also observed. These results demonstrate substantial non-olfactory afferent projections to the telencephalon in ranid frogs.

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.

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.

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.

[Electrophysiological atlas of human thalamus and adjacent structures.--Microcomputer assisted mapping of neurophysiological data and its application to stereotaxic surgery].

During stereotaxic surgery anatomical structures and their extent on trajectories were identified by neural noise (field potential) obtained by semi-microelectrode technique. Locations of anatomical structures (the white mater, caudate nucleus, thalamus, subthalamic field and nuclei in the subthalamic field) were fed into microcomputer (NEC PC-8001) as 3 dimensional correlates and stored in minifloppy disc system (NEC PC-8031). Data with satisfactory recordings from 48 trajectories from 30 patients (18 parkinsonism, 5 central pain, 7 others) entered this study. Microcomputer was so programmed that locations of the trajectories and electrophysiologically identified anatomical structures at that location in various coronal, sagittal and horizontal planes were displayed. Accumulation of this display from various groups of patients automatically created electrophysiological atlas. For comparison of thus created electrophysiological atlas with anatomical atlas display was made on various sections of the Schaltenbrand and Bailey's Atlas which were also stored in the mimifloppy disc system. Electrophysiological topography of the thalamus and adjacent structures was reasonably similar to anatomical topography with minor, but significant individual variations. In most cases the ventral border of the thalamus was located in the close vicinity of CA-CP line, however, in some cases the thalamus was located deep into the subthalamic field. This was thought to be due to the difficulty in identifying the ventral border of the thalamus by this technique and in such occasions other neurophysiological method for identifying the ventral border of the thalamus, i.e., thalamocortical evoked potential and other stimulation technique, were necessary. Medial aspect of the V. im. nucleus emitted neural noise of different characteristics which in current program was recognized as the subthalamic field. This implies that the medial and lateral aspects of the V. im. nucleus are cytoarchitecturally different and that it is possible to differentiate the medial and lateral aspects of the V. im. nucleus by this technique. The lateral thalamic border, i.e., thalamocapsular border, also showed relatively wide range of individual variations. When various parameters including age, sex, diagnosis and width of the 3rd ventricles were examined for possible cause of these variations, a tendency was noted that the thalamocapsular border was medially placed when the width of the 3rd ventricle was small. In this system it is possible to display sequentially electrophysiologically identified structures along any trajectory. This display method, which was called "tract study," was very usefull for comprehensive understanding of location of trajectory in relation to individually varying anatomical structures...

[Combined (surgical and drug) therapy of parkinsonism]. / Kombinirovannoe (khirurgicheskoe i medikamentoznoe) lechenie parkinsonizma.

Stereotaxic surgical operations on the basal cerebral ganglia are effective in the tremor and tremor-rigid forms of parkinsonism. Surgery is followed by an increased excretion of dopamine with a good clinical effect in most cases. Madopar (L-DOPA with an inhibitor DOPA-decarboxylase) is most effective in the akinetic and rigid-akinetic forms of the disease. Prolonged treatment with this drug leads to a sharp increase in DOPA and less significant in dopamine secretion. The effect of a single low dose of madopar on DOPA and dopamine excretion can be detected for six hours. When stereotaxic operation is indicated, the combined (surgery plus drug therapy) treatment of parkinsonism is most optimal. Following effective stereotaxic surgery, drug therapy should be continued with reduced dosage of the drugs.

[Effect of single-stage stereotaxic destruction of Forel's field H on neurologic functions and the structure of paroxysms in patients with generalized epilepsy]. / Vliianie odnomomentnoi stereotaksicheskoi destruktsii polia Forelia H na nevrologicheskie funktsii i strukturu paroksizmov u bol'nykh generalizovannoi épilepsiei.

The structure and frequency of epileptic paroxysms and neurologic symptoms were analyzed in nine patients with generalized epilepsy in the early period after one-stage stereotactic Forel-H-destructions. The inhibitory influence of the operation on epileptic activity in this period is demonstrated and the variants of neurologic deficit are depicted. The early post-stereotactic investigations are shown to be promising for improving the efficacy of surgical treatment of generalized epilepsy and for gaining a better insight into Forel-H-functions.

[Stereotaxic method of treating extrapyramidal spastic torticollis]. / Stereotaksicheskii metod lecheniia ékstrapiramidnoi spasticheskoi krivoshei.

A total of 196 stereotaxic operations were performed on different subcortical structures (ventrooral thalamic nuclei, subthalamic area, Cajal's nucleus) in 152 patients with various forms of extrapyramidal spasmodic torticollis. A classification of the various forms of torticollis is suggested and 4 degrees of severity of the disease are distinguished. Study of the late results showed stable and marked improvement or practical recovery in more than 50 per cent of patients. Bilateral stereotaxic operations produce a good stable effect twice as often as unilateral operations (68% of patients). The choice of the side on which the first operation will be performed should be based on the suggested classification of the forms of the disease with due account for the predominant affection of different groups of muscles on one or both sides.

[Stereotaxic destruction of the interstitial nucleus of Cajal on spastic torticollis]. / Stereotaksicheskaia destruktsiia interstitsial'nogo iadra Kakhala pri spasticheskoi krivoshee.

Intraoperative clinical effects and the results of destruction were demonstrated in 31 patients with various forms of torticollis spastica subjected to operation on the interstitial nucleus of Cajal. The intraoperative clinical complex of symptoms was formed of changes of the toxic and clonic activity of the neck muscles and transient oculomotor and vestibular signs. The favourable postoperative results are evidence of the direct relation of the nuclear structures in the region of the posterior commissure to the mechanisms regulating the posture of the head and neck. Their exclusion may be one of the components of surgical correction of motor abnormalities in patients with torticollis spastica. These operations are more effective in the tonic form of the disease and in prevalence of the rotatory component in the impaired posture of the head.

[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.

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.