Applied Microanatomy Of Pituitary Stalk And Protection Strategy In Sellar Tumor Resection

Part1Study on Applied Microanatomy of Pituitary StalkPurpose: To study the microanatomy of pituitary stalk and surrounding structures incadaver skull specimens, so as to provide important microsurgical anatomy data ofidentifying and protecting pituitary stalk for transcranial surgery on sellar tumor.Methods: A total of17formalin fixed specimens of adult cadaver skull were selected,immersed in hot water (50℃) and soaked for30min. After that, the common carotidartery and the vertebral artery were rinsed with fresh water,10%ammonia water andhydrogen peroxide repeatedly, and then10%red gelatin solution was injected by pressurethrough the common carotid artery and vertebral artery. By using routine anatomy method,braincap was sawed off, and then the cerebral flax and parietal dura mater were removed.Afterwards, brain tissues above pituitary stalk were removed first to observe themorphology of optic chiasma and pituitary stalk and measure their lengths. Next, the opticchiasma, supraclinoidal portion of internal carotid artery, oculomotor nerve and trochlearnerve were cut off, and cerebral peduncle was transected, retaining the complete structureunder tentoriumcerebelli; telencephalon was taken, and then the position, morphology andtrend of pituitary stalk, as well as its relationship with diaphragma sellae hole and opticchiasma were further observed with naked eyes and surgery microscope, which were alsomeasured and recorded.Results: The pituitary stalk in specimens was brown, with the length of (9.4±2.6) mm.It was thick in upper part and thin in lower part with left right diameter of (3.4±0.6) mm inupper end and (2.4±0.5) mm in bottom end. The horizontal plane of pituitary stalkmidpoint of15cases was thinner than basilar artery, and that of2cases was as sick as basilar artery. From the coronal view, pituitary stalks of14cases were in the middle,extremitas inferiors of2cases were slightly skewed to the right, and1case was skewed tothe left. From sagittal view, pituitary stalks of all cases tilted towards front lower from theend of hypothalamus,11cases of pituitary stalks were relatively straight,6cases ofpituitary stalks were tortuous in front and back, among which,2cases were closelyassociated with saddle back, curving backward with an angle in the saddle back. Opticchiasma of1case (5.9%) located above the tuberculum sellae,2cases (11.8%) above thesaddle back; the1st space covered an area of (28.4±6.2mm2). Pituitary stalk wassurrounded by arachnoid and fixed by many fibrous trabeculae. Blood vessels were rich:Superior hypophysial artery and inferior hypophysial artery were mainly involved in bloodsupply; the total number of uperior hypophysial artery was92,2.7(14) on each side onaverage; the emergence rate of inferior hypophysial artery on each side was100%.Diaphragma sellae holes were usually circular, with apertures of (7.1±1.6) mm,94.1%ofwhich were greater than5mm.Results: The microanatomy study provides important information about anatomicalstructures and anatomical parameters of pituitary stalk and its surrounding structures, aswell as the anatomical relationship among them. Pituitary stalk, connecting hypothalamusand pituitary, is thick in upper part and thin in lower part, being straight mostly; it locatesin the center of diaphragma sellae hole, surrounded by arachnoid, with fixed superiorhypophysial artery and inferior hypophysial artery for blood supply. All the structuresabove offer effective theoretical guidance for identifying and protecting pituitary stalk andother structures in the operation. In addition, during operation, the growth pattern of tumorshould also be considered to determine the position of pituitary stalk. Different spaceoperations, applying sharp dissection along the arachnoid interface, reducing stretch andprotecting hypophyseal artery and perforator artery are conducive to protect the function ofpituitary stalk, so as to reduce the occurrence of surgical complications. Part2. Identification and Protection Strategy of Pituitary Stalks inTranscranial Saddle Tumor ResectionPurpose: Lesions learned from different saddle tumor resections and discussionsabout identification and protection of pituitary stalks in surgery.Methods: Retrospective analysis of clinical data of110cases with sellar regiontumors. The cases were selected form neurosurgery department of the Second AffiliatedHospital of Soochow University and Weifang People’s Hospital. The patients weretranscranial operated and stayed in hospital from January2008to December2011. Thedata were complete and the descriptions of pituitary stalks were very particularly recordedin operative logs. Pterional approach were used in34cases, subfrontal approach in21cases, supraorbital keyhole approach in20cases, interhemispheric approach in35cases(21used fronto basal interhemispheric approach,9used interhemispheric trans laminaterminalis approach,5used trans callosum hemispheres approach). Preoperative bycraniocerebral MRI scanning, the position of pituitary stalk was clear determined in53cases, might be the signal of pituitary stalk in25cases, not found in32cases.Results:47pituitary adenoma cases,42of them had complete resections,4subtotalresections, and1partial resection.44cases had well remained pituitary stalks (93.6%),2were partially remained because of tumor erosion,1was undiscovered. Serum electrolytedisorder occurred in7cases, all were corrected in short time. Concurrent diabetes insipidusoccurred in34cases,21of them returned to normal in1or2weeks after operations,10were recovered3months later. In the9to24months follow up, persistent diabetesinsipidus occurred in3cases, patients were prescribed with oral desmopressin to controlthe symptom.38craniopharyngioma cases,32of them had complete resections,6subtotalresections.27cases had well remained pituitary stalks (73.7%),2were anatomicalpreserved because of tumor erosion,5were partially remained and4were undiscovered.Serum electrolyte disorder occurred in13cases, they were totally corrected when they left hospital. Concurrent diabetes insipidus occurred in27cases,10of them returned to normalin3weeks,7were recovered in3months. In the3to48months follow up, persistentdiabetes insipidus occurred in10cases, patients were prescribed with oral desmopressin tocontrol the symptom.25meningioma cases,23of them had complete resections,21subtotal resections.24cases had well remained pituitary stalks (96%),1was anatomical preserved. No serumelectrolyte disorder occurred. Transient diabetes insipidus occurred in5cases; theyrecovered in13weeks.No deaths in all cases.1pituitary adenoma and1craniopharyngioma were relapsedduring the follow up, both were performed gamma knife radiosurgery.Conclusion: The micro anatomical study of pituitary stalk can provide theoreticalbasis on identification and protection of pituitary stalk in sellar tumor resection. For theposition of pituitary stalk, it can be initially determined by brain Magnetic ResonanceImaging (MRI) before operation and further identified based on the structures ofhypothalamic eminent infundibulum, diaphragma sellae hole, surface vein striae medullaris,superior hypophysial artery and so forth during operation. When separating posterior wallof tumor, sharp dissection must be conducted carefully along the arachnoid interface toprevent feeding artery injury due to over stretch and fulguration. The retention of thepituitary stalk is directly associated with the nature of tumor (P=0.003). However, there isno obvious difference in the four kinds of surgical approaches (P=0.850). The usage ofCUSA can positively protect the pituitary stalk. Whether the pituitary stalk can be retainedand the damage extent can directly influence the incidence and recovery time ofpostoperative diabetes insipidus. Those who retain the pituitary stalk well will experiencediabetes insipidus and recover after about2weeks, accounting for66.7%(34/51) of thetotal number of diabetes insipidus. If the pituitary stalk is damaged or dissected, the time ofdiabetes insipidus is long, and the patients recover after about3months. Those whosepituitary stalks are severely damaged or partially retained experience persistent diabetesinsipidus. The appropriate surgical approach is chosen according to the location, size, growthdirection of the tumor and the optic chiasm location. Approach of basis frontalis orlongitudinal fissure approach of basis frontalis is suitable for people whose tumor grows inanterior skull base and cranial saddle, which is mainly operated in the first space. When thetumor bulges to optic chiasma and the distance between the third ventricle or optic chiasmaand tuberculum sellae is less than2mm, operations should be made in the fourth space,approaching from basis frontalis and the end plate of interhemisphere fissure. Supraorbitalkeyhole approach has a minimally invasive characteristic and it is an improvement of basisfrontalis approach. Along with the development of technology, most lesions in the sellarregion can be handled. Keyhole approach is not favorable when the tumor obviously growsto one side of the sellar region, or even bulges to the temporal lobe or third ventricle.Pterion approach should be adopted when the tumor grows obviously laterally andoperated mainly in the second and third space, the first space can also be considered.Skillful surgical techniques play an important role in the identifying and protecting of thepituitary stalk, reducing the incidence of surgical complications and the recovery of thepatients.