The Rhomboid Lip: Anatomy, Pathology, and Clinical Consideration in Neurosurgery.

OBJECTIVE: To describe microsurgical anatomy of the rhomboid lip (RL) and to consider its role by presenting histology and clinical cases. METHODS: We examined 10 (20 sides) formalin-fixed adult human cadaveric heads injected with colored silicone. A total of 20 RLs were examined posteriorly. We examined the expansion of the RL in the cerebellopontine cistern. We assessed the relationship between the RL and choroid plexus and the RL and cranial nerve IX and classified the RL. We also observed these relationships in clinical cases during surgeries and examined histologic assessments of the RL. RESULTS: The RL was divided into 3 types, non-extension type, lateral extension type, and jugular foramen type, according to the relationship between the RL and choroid plexus. There were many variations of the extension of the RL. The jugular foramen type was rare. CONCLUSIONS: Histologically, the RL is the remnant of the fourth ventricle covered with ependymal cells. Knowledge of the detailed anatomy and proper dissection of the RL may help surgeons to obtain good visualization of structures around the foramen of Luschka.

A new protocol to treat moderate to severe intraventricular hemorrhage with obstructive hydrocephalus.

OBJECTIVES: For patients with intraventricular hemorrhage (IVH) accompanied by obstructive hydrocephalus, external ventricular drainage (EVD) alone is proven to be often insufficient, and lumbar drainage (LD) is proven promising but considered contraindicative in the acute phase. The objective was to analyze the safety and feasibility of treatment for IVH with early continuous LD (CLD) in addition to open EVD regardless of the presence of acute obstructive hydrocephalus. METHODS: In this prospective study, 10 consecutive patients with moderate to severe IVH received emergency EVD and early CLD insertion regardless of the presence of obstructive hydrocephalus or blood clots in the third and fourth ventricles. During the whole course of treatment, the EVD was kept open at a safe height until replaced by CLD alone. When the drained CSF from CLD was nearly normal, gradual weaning of the CLD was attempted. Ventriculoperitoneal (VP) shunt would be performed if there was evidence of communicating hydrocephalus. RESULTS: In all the cases, EVD could be safely replaced by CLD alone. There was no evidence of axial herniation or infection, and no requirement of EVD revision. After CLD weaning, only two patients underwent VP shunt procedure. Follow-up study on 3 months and 6 months demonstrated that 7 (70%) patients had good (Glasgow Outcome Scale (GOS) 4 to 5) outcome and 1 (10%) patient died 1 month after discharge due to renal failure. CONCLUSIONS: RESULTS suggest that this new therapy which combines EVD with early CLD insertion is safe and easy to manage moderate to severe IVH with obstructive hydrocephalus.

Efficacy and safety of key hole craniotomy for the evacuation of spontaneous cerebellar hemorrhage.

The efficacy and safety of cerebellar hemorrhage evacuation by key hole craniotomy and the importance of thorough evacuation and irrigation of the hematoma in the fourth ventricle to resolve obstructive hydrocephalus were assessed in 23 patients with spontaneous cerebellar hemorrhage (SCH) greater than 3 cm or with brainstem compression and hydrocephalus. A 5-cm elongated S-shaped scalp incision was made, and a 3-cm key hole craniotomy was performed over a cerebellar convexity area. The hematoma was immediately evacuated through a small corticotomy. The hematoma in the fourth ventricle was gently removed through the hematoma cavity, followed by thorough saline irrigation to release obstructive hydrocephalus. Patients classified retrospectively into favorable and poor outcome groups using the Glasgow Outcome Scale (GOS) scores of 4-5 vs. 1-3 showed significant differences with respect to the preoperative Glasgow Coma Scale, hematoma size and volume, and brainstem compression. Only 2 of the 23 patients required ventricular drainage and no postoperative complications were recorded. Patients treated by experienced and inexperienced surgeons showed no significant differences in the hematoma evacuation rate, postoperative GOS, and interval from skin incision to start of hematoma evacuation. Our simplified method of key hole craniotomy to treat SCH was less invasive but easy to perform, as even inexperienced neurosurgeons could obtain good surgical results. Thorough cleaning of the fourth ventricle minimized the necessity for ventricular drainage.

Ruptured aneurysms of the choroidal branches of the posterior inferior cerebellar artery: a review of the literature and a case report.

Aneurysms of the choroidal branches of the posterior inferior cerebellar artery (PICA) are quite rare; only seven such cases have been reported thus far. In this study, we present a very rare case of a ruptured aneurysm of a choroidal branch of the PICA; the aneurysm was exposed by splitting the vermis and resected after proximal arterial ligation. We have also undertaken a thorough review of the literature on aneurysms in choroidal branches of the PICA, focusing on the clinical presentation, etiology, radiological findings, and surgical strategies. We found that the aneurysms in our patient and the aneurysms in seven published case reports were small, and frequently associated with vascular anomalies. Intraventricular hemorrhage (IVH) in the fourth ventricle was detected in all eight cases. The outcomes of surgical treatment were generally favorable, notwithstanding the high incidence of rebleeding after rupture of distal PICA aneurysms. The recognition of predominant fourth ventricular hemorrhage should raise the suspicion of the presence of an underlying aneurysm, and digital subtraction angiograms (DSAs) should be immediately obtained in order to detect small aneurysms of the choroidal branches of the PICA.

Clinical and surgical features of lower brain stem hemangioblastomas in von Hippel-Lindau disease.

BACKGROUND: In the context of von Hippel-Lindau disease (VHL), the medulla oblongata is a relatively frequent site of growth of hemangioblastomas, posing related clinical and surgical difficulties. Their management requires a close correlation between clinical evolution and morphological surveillance. In order to describe their clinical and surgical features, we reviewed our experience in the treatment of these lesions. METHODS: Between 2001 and 2009, 14 patients (9 female and 5 male, mean age 34 years) underwent removal of 15 lower brain stem hemangioblastomas. Based on the review of the clinical records and outpatient long-term follow-up visits, their clinical course was analyzed. Functional evaluation was measured with the Karnofsky Performance Scale (KPS) on admission, at discharge and at the last follow-up. The mean follow-up period was 30.8 months (range 4-99). RESULTS: All the operated hemangioblastomas were located in the dorsal medulla oblongata, in the context of multiple lesions, cerebellar and/or spinal. In ten patients hemangioblastomas were located in a median position at the obex area; in four cases a lateral location was observed. Cystic component was absent in two cases. Clinical onset preceded surgery by a mean of 8.5 months. Preoperatively three patients showed a KPS lower than 80, ten patients between 80 and 90, and one patient scored 100 (asymptomatic). There was no surgical mortality. Nine out of 14 patients showed a temporary surgical morbidity. One patient required a tracheostomy. At follow-up ten patients scored a KPS better than before the operation, while the other four patients remained stable. Permanent morbidity was observed in three patients. CONCLUSIONS: Lower brain stem hemangioblastomas in the context of VHL show an often gradual onset of signs and symptoms except for patients who develop an obstructive hydrocephalus. Although transient surgical complications are possible, surgery provides favorable long-term results.

[Three cases of small brain infarction in the lateral wall of the fourth ventricle presenting with paroxysmal positional vertigo and vomiting].

A lesion responsible for central paroxysmal positional vertigo (PPV) is often found in the dorsolateral wall of the fourth ventricle. A relatively large tumor or hemorrhage in the dorsolateral wall of the fourth ventricle usually causes central PPV, but small brain infarction has hardly been reported to cause central PPV. We report three cases of a small brain infarction in the lateral wall of the fourth ventricle presenting with central PPV. All of the cases showed similar clinical features in which a given recumbent position and a sitting position caused a dizziness associated with nausea and vomiting over an acute period. The symptom lasted one to two months after the onset. In two of our cases, no neurological abnormal signs, except nystagmus, were observed, and initial differentiation of central PPV from peripheral PPV was difficult. Interruption of the vestibular nuclei-archicerebellar loop seems to be responsible for the central PPV. Recognition of the clinical features of central PPV and diffusion-weighted MRI images are important for a precise local diagnosis in small brain infarction showing PPV.

Los recesos del IV ventrículo / IV ventricle recesses

Objetivo: Analizar la anatomía de los recesos del IV ventrículo y su relación con las vías de abordaje. Método. Se disecaron 3 especímenes de cerebelo en forma sistemática. Se utilizó la técnica de Klinger para las fibras y la cavidad se estudió en 2 moldes de acrilico. Se realizó un análisis bibliográfico. Resultados: Los moldes dieron una idea cabal de los recesos, su ubicación espacial y forma. Hay uno impar, el posterior, ubicado en la línea media y dos pares de recesos simétricos: los posterolaterales, ubicados a los del primero y algo por debajo del mismo, y los laterales, conductos que abrazan la unión bulbo protuberancial y se abren al ángulo bulbo pontocerebeloso por el agujero de Luschka. Para estudiar las relaciones de estas estructuras "in situ" fue útil extirpar primero las amígdalas. El techo de los recesos laterales está constituido por fibras cocleares en su parte medial y el pedúnculo del flóculo en su parte lateral. El núcleo dentado está separado del receso posterolateral por fibras del pedúnculo del flóculo. Conclusión. El IV ventrículo tiene 5 recesos. Los moldes del ventrículo permitieron tener una idea más clara de la disposición tridimensional de ellos. El conocimiento anatómico permitió un abordaje racional y menos traumático para lesiones del IV ventrículo o las estructuras vecinas. Palabras clave: IV ventrículo - flóculo - receso posterolateral.

Objective: To study the anatomy of the anatomy of the IV ventricle recesses and their relationship to the surgical approaches. Methods: Three specimens of brain stem and cerebellum were prepared sistematically and the fiblers were dissected with the Klinger's method. Two acrylic casts were obtained in order to analyze the cavity shape details of the IV ventricle. Results: The recesses of the IV ventricle are better understood by the inspection of the casts. In the midline lies the posterior recess. There are two pairs of symmetrical recesses: the posterolateral and the lateral. The laters, are two ducts that drain into the cerebello ponto medullary angle through the foramina of Luschka. The excision of the amigdala helps to study the anatomical relations "in situ". The roof of the lateral recess is made up by cochlear fibers and the flocculus penduncle laterally. The dentate nucleus us separated from the posterolateral recess by fibers from the flocculus pedicle. Conclusion: the IV ventricle has five recesses. Casts of the ventricle gave a better idea of their tridimensional disposition and relationships. With a proper anatomical knowledge, a rational non traumatic access to the different structures can be achieved. Key words: flocculus, IV ventricle, posterolateral recess.

Multiple de novo vascular malformations in relation to diffuse venous occlusive disease: a case report.

Brain vascular malformations are dynamic disorders. Although mostly considered to be of congenital origin, the improvement of clinical imaging and vasculogenesis knowledge has shown that they might also result from a biological dysfunction of the remodeling process after birth. Venous occlusive disease and ishemia may represent powerful revealing triggers and support the capillary venous origin of some vascular malformations. We report a unique case of the development of multiple de novo vascular malformations (transverse sinus dural fistula and posterior fossa cavernomas) following acoustic neuroma surgery.

Comparison of the transvermian and telovelar approaches to the fourth ventricle.

OBJECT: The two most common surgical routes to the fourth ventricle are the transvermian and telovelar approaches. The purpose of this study was to compare the microanatomy and exposures gained through these approaches. METHODS: Ten formalin-fixed specimens were dissected in a stepwise manner to simulate the transvermian and telovelar surgical approaches. Stealth image guidance was used to compare the exposures and working angles obtained using these approaches. The transvermian and telovelar approaches provided access to the entire rostrocaudal length of the fourth ventricle floor from the aqueduct to the obex. In addition, both approaches provided access to the entire width of the floor of the fourth ventricle. The major difference between the two approaches regarded the exposure of the lateral recess and the foramen of Luschka. The telovelar, but not the transvermian, approach exposed the lateral and superolateral recesses and the foramen of Luschka. The transvermian approach, which offered an incision through at least the lower third of the vermis, afforded a modest increase in the operator's working angle compared with the telovelar approach when accessing the rostral half of the fourth ventricle. CONCLUSIONS: The transvermian approach provides slightly better visualization of the medial part of the superior half of the roof of the fourth ventricle. The telovelar approach, which lacks incision of any part of the cerebellum, provides an additional exposure to the lateral recesses and the foramen of Luschka.

[The structural organization of the normal rat area postrema and under conditions of chronic exposure to gravitational loads]. / Strukturnaia organizatsiia area postrema krysy v norme i v usloviiakh khronicheskogo vozdeistviia gravitatsionnykh peregruzok.

Topography and structure of rat area postrema were specified using light optic and electron microscope. Disturbance of liquor-encephalic transport (hydrops of ependymocytes), sharp changes of cytoplasmic organelles in neurons, signs of intercellular desintergration (synapse degeneration after "clear" type), death of part of neurons, disorder in secretory processes in neuroendocrine cells were shown to occur following chronic effect of gravitation overloads, in its structural elements. These changes take place on the background of hemomicrocirculatory disturbances, appearance of connective tissue fibres in perivascular space of Virchow-Robin and are probably conditioned by a developing circulatory hypoxia.

Telovelar approach to the fourth ventricle: microsurgical anatomy.

OBJECT: In the past, access to the fourth ventricle was obtained by splitting the vermis or removing part of the cerebellum. The purpose of this study was to examine the access to the fourth ventricle achieved by opening the tela choroidea and inferior medullary velum, the two thin sheets of tissue that form the lower half of the roof of the fourth ventricle, without incising or removing part of the cerebellum. METHODS: Fifty formalin-fixed specimens, in which the arteries were perfused with red silicone and the veins with blue silicone, provided the material for this study. The dissections were performed in a stepwise manner to simulate the exposure that can be obtained by retracting the cerebellar tonsils and opening the tela choroidea and inferior medullary velum. CONCLUSIONS: Gently displacing the tonsils laterally exposes both the tela choroidea and the inferior medullary velum. Opening the tela provides access to the floor and body of the ventricle from the aqueduct to the obex. The additional opening of the velum provides access to the superior half of the roof of the ventricle, the fastigium, and the superolateral recess. Elevating the tonsillar surface away from the posterolateral medulla exposes the tela, which covers the lateral recess, and opening this tela exposes the structure forming the walls of the lateral recess.