Impact of target exposure via retrosigmoidal approach in surgical injury measured by virtual reality skill / 中华神经医学杂志

Objective To discuss the impact of target exposure via retrosigmoidal approach in surgical injury based on virtual reality anatomic models.Methods CT and MR imaging data of 15 adult cadaver heads were utilized to establish three-dimensional anatomy models of petrous bone.Surgical routes exposing different targets though retrosigmoidal approach were simulated by selecting osseous landmark points on the calvaria and skull base.Special form and sequence of anatomic structures in different routes were observed.Volumes of anatomic tissues were measured.Results All the surgical routes passed below the transverse sinus and lateral to the cerebellum.Route a exposed the lower cranial nerve and anterior inferior cerebellar artery;when reached the jugular tubercle,the route exposed inferior petrous sinus.Route b exposed the anterior inferior cerebellar artery,labyrinth and facial-acoustic nerve complex.Route c passed the medial to the superior petrous sinus and exposed the facial-acoustic nerve complex;when being arrived at petrous apex,the route exposed the trigeminal nerve,superior cerebellar artery and cavernous sinus.The volumes of the lower cranial nerve,osseous structures,cerebellum and artery were significantly different in models adopted different routes (P＜0.05);the volume of the lower cranial nerve was as follows:route c＞route a＞route b,the volume of osseous structures was as follows:route c ＞route b＞route a,the volume of cerebellum was as follows:route b ＞route a＞route c,and the volume of artery was as follows:route a ＞route c＞route b.Venous structure involved in route a ([68.91 ±1.91] mm3) was larger than that in route c ([248.92±11.26] mm3) with statistical significance (P＜0.05),and route b did not involve venous structure.Conclusions Targets in skull base has significant impaction on the size of anatomic structures involved in the route of retrosigmoidal approach.Relationship between injury and exposure can be evaluated objectively by the volume measurement.

The localization of the asterion according to the anatomical landmarks of posterior cranial fossa in newborns: clinical implications / Localización del asterión de acuerdo con los puntos anatómicos de la fosa craneal posterior en recién nacidos: implicaciones clínicas

The purpose of this study was to determine the localization of the asterion according to the anatomical landmarks of posterior cranial fossa and its relation with sinuses for posterolateral surgical approaches in newborns. On 70 head-halves, a needle about 2 mm with diameter was placed on the centre point of asterion (posterolateral fontanel) by inserting into the whole cranial bony tissue by forming an right angle with the bony surface. Various localizations of asterion and its measurements from the internal and external anatomical landmarks were investigated on term neonatal cadavers. The localization of asterion was found as on the sigmoid-transverse sinus junction (STJ) (5., 6., 7., 8. squares) in 40% of cases on right side and in 34%, on left side. Additionally, it was located below the STJ (9., 10., 11., 12. squares) in 60% of cases, on right side and in 63% of cases on left side. We determined that the most frequent localization of asterion as the 11. square both for the right and left sides 12 (34%) cases for the right side and 11 (31,4%) cases for the left side. The asterion was not located on 1., 2., 3., 4., 5. and 12. squares on right side and 1., 3., 4., 8. and 9. squares on left side. It has been found that the region of asterion has an average distance value of 19.9 mm to internal acoustic meatus (MI), 31.7 mm to posterior clinoid process (PC), 34.4 to dorsum sellae (DS), 19.2 mm to jugular foramen (FJ), 23.0 mm to hypoglossal canal (HC), internally. The distance of asterion as 28.8 mm to zygoma root (ZR) and 22.3 mm to Henle's spine (HS) and 15.8 mm to mastoid tip (MT) and 35.9 mm to external occipital protuberance (PE) were observed. By the guide of point asterion on newborns the area of 1cm2 on this point which was placed on superior 4 squares of our scale diagram is suggested as a safe area of placement of first burr hole to avoid from the risk of bleeding of sigmoid and transverse sinuses on craniotomies of posterior fossa.

El propósito de este estudio fue determinar la localización del asterion de acuerdo con los puntos anatómicos de la fosa craneal posterior y su relación con los senos de abordajes quirúrgicos posterolaterales en los recién nacidos. Fueron utilizadas 70 hemicabezas y se colocó una aguja de alrededor de 2 mm de diámetro en el punto central del asterion (fontanela posterolateral) en todo el tejido óseo craneal produciéndose la formación de un ángulo recto con la superficie ósea. La localización del asterion y las mediciones de los puntos de referencia anatómicos internos y externos fueron investigados en cadáveres de neonatos a término. La localización del asterion se encontró en la unión sinusal transverso sigmoide (STJ) (cuadrados 5., 6., 7., 8.) en el 40% de los casos en el lado derecho y en el 34%, en el lado izquierdo. Además, se encontró por debajo del STJ (cuadrados 9., 10., 11., 12.) en un 60% de los casos en el lado derecho y en el 63% de los casos en el lado izquierdo. Se determinó que la localización más frecuente del asterion fue 11., tanto para los lados derecho e izquierdo, 12 casos (34%) para el lado derecho y 11 casos (31,4%) para el lado izquierdo. El asterion no se encuentra en los cuadrados 1., 2., 3., 4., 5. y 12. del lado derecho y 1., 3., 4., 8. y 9. del lado izquierdo. Se determinó que la región del asterion tiene una distancia promedio de 19,9 mm al meato acústico interno, 31,7 mm al proceso clinoides posterior, 34,4 mm al dorso selar, 19,2 mm al foramen yugular y 23,0 mm al canal hipogloso, internamente. La distancia del asterion a la raíz del hueso cigomático fue 28,8 mm y 22,3 mm a la columna vertebral, siendo de 15,8 mm al proceso mastoides y 35,9 mm a la protuberancia occipital externa. En los recién nacidos, se sugiere un área de 1cm2 y se colocan en 4 casillas superiores de nuestro diagrama a escala, como una zona segura para la realización de la primera trepanación para evitar el riesgo de sangrado de los senos sigmoide y transverso en craneotomías de fosa posterior.

Quistes epidermoides del ángulo pontocerebeloso: experiencia en 43 casos con seguimiento a largo plazo / Cerebellopontine angle epidermoid cysts: experience of 43 cases with long-term follow-up

Introducción: El quiste epidermoide ocupa el tercer lugar de los tumores en la región del ángulo pontocerebeloso. El presente informe describe los principales aspectos clínicos, radiológicos y el manejo quirúrgico de este tipo de quistes en esa ubicación. Material y métodos: Serie de pacientes operados de quiste epidermoide del ángulo pontocerebeloso entre 1998 y 2005. Se clasificó la extensión de la lesión según las cisternas involucradas: extensión I, limitada al ángulo pontocerebeloso; extensión II, cisternas ángulo pontocerebeloso + supraselar + perimesencefálicas; extensión III, ángulo pontocerebeloso con extensión paraselar y temporomesial. Resultados: 43 pacientes con seguimiento promedio de 85 meses, la edad media fue de 34 años; 67 % fue del sexo femenino. Los principales síntomas fueron cefalea (58.1 %) y afección trigeminal (41.8 %). De acuerdo con nuestra clasificación, los pacientes con extensión temporomesial (25.6 %) presentaron mayor incidencia de epilepsia secundaria (p = 0.001), y aquellos con neuralgia del trigémino tuvieron lesiones más limitadas al ángulo pontocerebeloso (p = 0.006). El abordaje más empleado fue el retrosigmoideo (39.5 %); la resección tumoral fue completa en 65 % de los pacientes. Conclusiones: Existen diferencias en la presentación clínica, grado de resección quirúrgica y recurrencia tumoral entre las diferentes extensiones del quiste epidermoide del ángulo pontocerebeloso, por lo que se requiere abordaje terapéutico específico. Para que las comparaciones entre series sea válida, es deseable el consenso y la elaboración de una clasificación consensuada acerca las extensiones del quiste epidermoide en esa ubicación.

BACKGROUND: Epidermoid tumors represent the third most common lesion of the cerebellopontine angle (CPA). Their evolution and clinical features are distinctively characteristic. We present a comprehensive review of the clinical, imaging and surgical aspects of epidermoid cysts of the CPA. METHODS: We conducted a case series of patients diagnosed with epidermoid cyst of the CPA who were operated on between 1998 and 2005. Lesions were classified according to their anatomic extent: grade I(-) within the boundaries of the CPA, grade II(-) extension to the suprasellar and perimesencephalic cisterns, and grade III(-) parasellar and temporomesial region involvement. RESULTS: This study was comprised of 43 patients with a mean follow-up of 85 months. Mean age was 34 years, and 67% of the patients were female. The initial symptom was headache in 58.1% of the cases and trigeminal neuralgia in 41.8%. According to our classification, temporomesial involvement (25.6%) was significantly (p = 0.001) associated with a higher incidence of seizures, and trigeminal neuralgia was present in patients with lesions limited to the CPA (p = 0.006). The lesions were reached essentially through a retrosigmoidal approach (39.5%) and surgical excision was deemed to be complete in 65% of the cases. CONCLUSIONS: Our grading classification according to the anatomic extension correlates well with clinical presentation, type of surgical approach and extent of surgical removal. It is desirable to reach a consensus on the classification of tumor extension.

The Causes and Treatment for Cerebrospinal Fluid Leak after Microsurgical Removal of Vestibular Schwannomas / 中国医师杂志

Objective To explore the causes and treatment for cerebrospinal fluid(CSF) leak after microsurgical removal of vestibular schwannomas(VS) with the suboccipital retrosigmoid approach.Methods A retrospective study was accomplished on 258 patients with VS operated through the suboccipital retrosigmoidal approach from Jan 1994 to Aug 2003.After operation,cerebrospinal fluid rhinorrhea occurred in 19 cases and subcutaneous retroauricular CSF leak occurred in 5 cases.Results In 14 cases the CSF leak was stopped after treatment by external lumbar cerebrospinal fluid drainage(CELCFD).Six patients were operated again with sealing the internal acoustic meatus and the mastoid cells with fibrin glue and muscle.The patients were followed up for 14 months to 8 years after treatment,and there was no recurrence of CSF leak or delayed onset meningitis.Conclusion CSF leak was the common complication after vestibular schwannoma removal and the most common reason was the drilled posterior wall of the internal acoustic meatus with opening of the mastoid cells.The closure of petrous air cells was very important to prevent its postoperative CSF leak.Most of the patients were successfully treated by external lumbar cerebrospinal fluid drainage and only a few cases needed revision surgery.