Миңінома: себептері, белгілері және емдеу жолдары

Type of tumor

Small tumors (e. g., < 2.0 cm) usually are incidental findings at autopsy without having caused symptoms. Larger tumors may cause symptoms, depending on the size and location. Focal seizures may be caused by meningiomas that overlie the cerebrum. Progressive spastic weakness in legs and incontinence may be caused by tumors that overlie the parasagittal frontoparietal region. Tumors of the Sylvian aqueduct may cause myriad motor, sensory, aphasic, and seizure symptoms, depending on the location. Increased intracranial pressure eventually occurs, but is less frequent than in gliomas. Diplopia (Double vision) or uneven pupil size may be symptoms if related pressure causes a third and/or sixth nerve palsy.

The causes of meningiomas are not well understood. Most cases are sporadic, appearing randomly, while some are familial. Persons who have undergone radiation, especially to the scalp, are more at risk for developing meningiomas, as are those who have had a brain injury. Atomic bomb survivors from Hiroshima had a higher than typical frequency of developing meningiomas, with the incidence increasing the closer that they were to the site of the explosion. Dental X rays are correlated with an increased risk of meningioma, in particular for people who had frequent dental X rays in the past, when the X ray dose of a dental X ray was higher than in the present. Having excess body fat increases the risk. A 2012 review found that mobile telephone use was unrelated to meningioma. People with neurofibromatosis type 2 (NF 2) have a 50% chance of developing one or more meningiomas. 92% of meningiomas are benign. 8% are either atypical or malignant.

Meningiomas arise from arachnoidal cap cells, most of which are near the vicinity of the venous sinuses, and this is the site of greatest prevalence for meningioma formation. Some subtypes may arise from the pial cap cells that migrate during the development together with blood vessels into the brain parenchyma. Other uncommon locations are the lateral ventricle, foramen magnum, and the orbit/optic nerve sheath. As such, they also have a tendency to calcify and are highly vascularized. Meningiomas often are considered benign tumors that can be removed by surgery, but most recurrent meningiomas correspond to histologic benign tumors. The metabolic phenotype of these benign recurrent meningiomas indicated an aggressive metabolism resembling that observed for atypical meningioma.

The risk of meningioma can be reduced by maintaining a normal body weight, and by avoiding unnecessary dental x rays.

Observation with close imaging follow up may be used in select cases if a meningioma is small and asymptomatic. In a retrospective study on 43 patients, 63% of patients were found to have no growth on follow up, and the 37% found to have growth at an average of 4 mm / year. In this study, younger patients were found to have tumors that were more likely to have grown on repeat imaging; thus are poorer candidates for observation. In another study, clinical outcomes were compared for 213 patients undergoing surgery vs. 351 patients under watchful observation. Only 6% of the conservatively treated patients developed symptoms later, while among the surgically treated patients, 5.6% developed persistent morbid condition, and 9.4% developed surgery related morbid condition. Observation is not recommended in tumors already causing symptoms. Furthermore, close follow up with imaging is required with an observation strategy to rule out an enlarging tumor.

Radiation therapy may include photon beam or proton beam treatment, or fractionated external beam radiation. Radiosurgery may be used in lieu of surgery in small tumors located away from critical structures. Fractionated external beam radiation also can be used as primary treatment for tumors that are surgically unresectable or, for patients who are inoperable for medical reasons. Radiation therapy often is considered for WHO grade I meningiomas after subtotal (incomplete) tumor resections. The clinical decision to irradiate after a subtotal resection is somewhat controversial, as no class I randomized, controlled trials exist on the subject. Numerous retrospective studies, however, have suggested strongly that the addition of postoperative radiation to incomplete resections improves both progression free survival (i. e. prevents tumor recurrence) and improves overall survival. In the case of a grade III meningioma, the current standard of care involves postoperative radiation treatment regardless of the degree of surgical resection. This is due to the proportionally higher rate of local recurrence for these higher grade tumors. Grade II tumors may behave variably and there is no standard of whether to give radiotherapy following a gross total resection. Subtotally resected grade II tumors should be radiated.

Likely, current chemotherapies are not effective. Antiprogestin agents have been used, but with variable results. A 2007 study of whether hydroxyurea has the capacity to shrink unresectable or recurrent meningiomas is being further evaluated.

Many individuals have meningiomas, but remain asymptomatic, so the meningiomas are discovered during an autopsy. One to two percent of all autopsies reveal meningiomas that were unknown to the individuals during their lifetime, since there were never any symptoms. In the 1970s, tumors causing symptoms were discovered in 2 out of 100,000 people, while tumors discovered without causing symptoms occurred in 5.7 out of 100,000, for a total incidence of 7.7/100,000. With the advent of modern sophisticated imaging systems such as CT scans, the discovery of asymptomatic meningiomas has tripled. Meningiomas are more likely to appear in women than men, though when they appear in men, they are more likely to be malignant. Meningiomas may appear at any age, but most commonly are noticed in men and women age 50 or older, with meningiomas becoming more likely with age. They have been observed in all cultures, Western and Eastern, in roughly the same statistical frequency as other possible brain tumors. Charles Oberling then separated these into subtypes based on cell structure and, over the years, several other researchers have defined dozens of different subtypes as well. In 1979, the World Health Organization (WHO) classified seven subtypes, upgraded in 2000 to a classification system with nine low grade variants (grade I tumors) and three variants each of grade II and grade III meningiomas. The first documented successful removal of a skull base meningioma was performed in 1835 by Zanobi Pecchioli, Professor of Surgery at the University of Siena. and to effectively differentiate between the different meningioma subtypes.

Leonard Wood (1860–1927), underwent successful surgery by Dr. Harvey Cushing for a meningioma circa 1910, a major advance in neurosurgery at the time. Elizabeth Taylor (1932–2011), American actress, underwent surgery in February 1997 to remove a benign meningioma. Kathi Goertzen (1958–2012), television news anchor in Seattle who underwent a very public battle with recurring tumors. She died on August 13, 2012, of complications related to her treatment. Eileen Ford (1922–2014), American model agency executive and co founder of Ford Models. Died on July 9, 2014, from complications of meningioma and osteoporosis. Mary Tyler Moore (1936–2017), American actress, underwent surgery in May 2011 to remove a benign meningioma. Jack Daulton (1956–), American trial lawyer and art collector, underwent three surgeries in 2011–2012 in connection with the removal of a golf ball size benign meningioma over his left motor cortex; he fully recovered without disability or recurrence. Simone Giertz (1990–), Swedish inventor and professional YouTuber, underwent surgery to remove a grade I meningioma in 2018 and radiation therapy after tumor regrowth in 2019.