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.

Gradient-Echo T2WI magnetic resonance imaging (MRI) is most sensitive method for diagnosing cavernous hemangiomas. MRI is such a powerful tool for diagnosis, it has led to an increase in diagnosis of cavernous hemangiomas since the technology's advent in the 1980s. The radiographic appearance is most commonly described as "popcorn" or "mulberry"-shaped. Computed tomography (CT) scanning is not a sensitive or specific method for diagnosing cavernous hemangiomas. Angiography is typically not necessary, unless it is required to rule out other diagnoses. Additionally, biopsies can be obtained from tumor tissue for examination under a microscope. It is essential to diagnose cavernous hemangioma because treatments for this benign tumor are less aggressive than that of cancerous tumors, such as angiosarcoma. However, since MRI appearance is practically pathognomonic, biopsy is rarely needed for verification.

Several different types of magnetic resonance imaging (MRI) may be employed in diagnosis: MRI without contrast, Gd contrast enhanced T1-weighted MRI (GdT1W) or T2-weighted enhanced MRI (T2W or T2*W). Non-contrast enhanced MRI is considerably less expensive than any of the contrast enhanced MRI scans. The gold standard in diagnosis is GdT1W MRI.

The reliability of non-contrast enhanced MRI is highly dependent on the sequence of scans, and the experience of the operator.

Diagnosis is generally made by magnetic resonance imaging (MRI), particularly using a specific imaging technique known as a gradient-echo sequence MRI, which can unmask small or punctate lesions that may otherwise remain undetected. These lesions are also more conspicuous on FLAIR imaging compared to standard T2 weighing. FLAIR imaging is different from gradient sequences. Rather, it is similar to T2 weighing but suppresses free-flowing fluid signal. Sometimes quiescent CCMs can be revealed as incidental findings during MRI exams ordered for other reasons. Many cavernous hemangiomas are detected "accidentally" during MRIs searching for other pathologies. These "incidentalomas" are generally asymptomatic. In the case of hemorrhage, however, a CT scan is more efficient at showing new blood than an MRI, and when brain hemorrhage is suspected, a CT scan may be ordered first, followed by an MRI to confirm the type of lesion that has bled.

Sometimes the lesion appearance imaged by MRI remains inconclusive. Consequently neurosurgeons will order a cerebral angiogram or magnetic resonance angiogram (MRA). Since CCMs are low flow lesions (they are hooked into the venous side of the circulatory system), they will be angiographically occult (invisible). If a lesion is discernible via angiogram in the same location as in the MRI, then an arteriovenous malformation (AVM) becomes the primary concern.

Cases of lymphangioma are diagnosed by histopathologic inspection. In prenatal cases, cystic lymphangioma is diagnosed using an ultrasound; when confirmed amniocentesis may be recommended to check for associated genetic disorders.

The auditory brainstem response (ABR) test gives information about the inner ear (cochlea) and nerve pathways for hearing via ongoing electrical activity in the brain measured by electrodes placed on the scalp. Five different waves (I to V) are measured for each ear. Each waveform represents specific anatomical points along the auditory neural pathway. Delays of one side relative to the other suggest a lesion in cranial nerve VIII between the ear and brainstem or in the brainstem itself. The most reliable indicator for acoustic neuromas from the ABR is the interaural latency differences in wave V: the latency in the impaired ear is prolonged. Different studies have indicated the sensitivity of ABR for detection of acoustic neuromas 1cm or larger to be between 90 and 95%. Sensitivity for neuromas smaller than 1cm are 63-77%. A newer technology, stacked ABR, may have sensitivity as high as 95% with specificity 88% for smaller tumors. ABR is considerably more cost effective, but MRI provides more information.

Stapedius reflex (SR) and caloric vestibular response (CVR) are non-invasive otologic tests for auditory neural function. These are not primary diagnostics for CPA neuromas, and are usually used in conjunction

with ABR.

In the treatment of a brain cavernous hemangioma, neurosurgery is usually the treatment chosen. Research needs to be conducted on the efficacy of treatment with stereotactic radiation therapy, especially on the long-term. However, radiotherapy is still being studied as a form of treatment if neurosurgery is too dangerous due the location of the cavernoma. Genetic researchers are still working on determining the cause of the illness and the mechanism behind blood vessel formation. Clinical trials are being conducted to better assess when it is appropriate to treat a patient with this malformation and with what treatment method. Additionally, long term studies are being conducted because there is no information related to the long-term outlook of patients with cavernoma. A registry exists known as The International Cavernous Angioma Patient Registry collects information from patients diagnosed with cavernoma in order to facilitate discovery of non-invasive treatments.

The Cognard et al. Classification correlates venous drainage patterns with increasingly aggressive neurological clinical course.

Cerebral angiography is the diagnostic standard. MRIs are usually normal.

The prognosis for lymphangioma circumscriptum and cavernous lymphangioma is generally excellent. This condition is associated with minor bleeding, recurrent cellulitis, and lymph fluid leakage. Two cases of lymphangiosarcoma arising from lymphangioma circumscriptum have been reported; however, in both of the patients, the preexisting lesion was exposed to extensive radiation therapy.

In cystic hygroma, large cysts can cause dysphagia, respiratory problems, and serious infection if they involve the neck. Patients with cystic hygroma should receive cytogenetic analysis to determine if they have chromosomal abnormalities, and parents should receive genetic counseling because this condition can recur in subsequent pregnancies.

Complications after surgical removal of cystic hygroma include damage to the structures in the neck, infection, and return of the cystic hygroma.

Depending on the grade of the sarcoma, it is treated with surgery, chemotherapy and/or radiotherapy.

From a pathology perspective, several tumors need to be considered in the differential diagnosis, including paraganglioma, ceruminous adenoma, metastatic adenocarcinoma, and meningioma.

Bilateral vestibular schwannomas are diagnostic of NF2.

NF II can be diagnosed with 65% accuracy prenatally with chorionic villus sampling or amniocentesis.

This is based on MRI scan, magnetic resonance angiography and CT scan. A cerebral digital subtraction angiography (DSA) enhances visualization of the fistula.

- CT scans classically show an enlarged superior ophthalmic vein, cavernous sinus enlargement ipsilateral (same side) as the abnormality and possibly diffuse enlargement of all the extraocular muscles resulting from venous engorgement.

- Selective arteriography is used to evaluate arteriovenous fistulas.

- High resolution digital subtraction angiography may help in classifying CCF into dural and direct type and thus formulate a strategy to treat it either by a balloon or coil or both with or without preservation of parent ipsilateral carotid artery.

The histology of EST is variable, but usually includes malignant endodermal cells. These cells secrete alpha-fetoprotein (AFP), which can be detected in tumor tissue, serum, cerebrospinal fluid, urine and, in the rare case of fetal EST, in amniotic fluid. When there is incongruence between biopsy and AFP test results for EST, the result indicating presence of EST dictates treatment. This is because EST often occurs as small "malignant foci" within a larger tumor, usually teratoma, and biopsy is a sampling method; biopsy of the tumor may reveal only teratoma, whereas elevated AFP reveals that EST is also present. GATA-4, a transcription factor, also may be useful in the diagnosis of EST.

Diagnosis of EST in pregnant women and in infants is complicated by the extremely high levels of AFP in those two groups. Tumor surveillance by monitoring AFP requires accurate correction for gestational age in pregnant women, and age in infants. In pregnant women, this can be achieved simply by testing maternal serum AFP rather than tumor marker AFP. In infants, the tumor marker test is used, but must be interpreted using a reference table or graph of normal AFP in infants.

Ferner et al. give three sets of diagnostic criteria for NF2:

1. Bilateral vestibular schwannoma (VS) or family history of NF2 plus Unilateral VS or any two of: meningioma, glioma, neurofibroma, schwannoma, posterior subcapsular lenticular opacities

2. Unilateral VS plus any two of meningioma, glioma, neurofibroma, schwannoma, posterior subcapsular lenticular opacities

3. Two or more meningioma plus unilateral VS or any two of glioma, schwannoma and cataract.

Another set of diagnostic criteria is the following:

- Detection of bilateral acoustic neuroma by imaging-procedures

- First degree relative with NF II and the occurrence of neurofibroma, meningiomas, glioma, or Schwannoma

- First degree relative with NF II and the occurrence of juvenile posterior subcapsular cataract.

The criteria have varied over time.

The incidence in the general population is roughly 0.5%, and clinical symptoms typically appear between 20 to 30 years of age. Once thought to be strictly congenital, these vascular lesions have been found to occur "de novo". It may appear either sporadically or exhibit autosomal dominant inheritance.

Diagnosis of IIA is based on finding an intracranial aneurysm on vascular imaging in the presence of predisposing infectious conditions. Positive bacterial cultures from blood or the infected aneurysm wall itself may confirm the diagnosis, however blood cultures are often negative. Other supporting findings include leukocytosis, an elevated erythrocyte sedimentation rate and elevated C-reactive protein in blood.

EST can have a multitude of morphologic patterns including: reticular, endodermal sinus-like, microcystic, papillary, solid, glandular, alveolar, polyvesicular vitelline, enteric and hepatoid.

Schiller-Duval bodies on histology are pathognomonic and seen in the context of the endodermal sinus-like pattern.

The tumor must be removed with as complete a surgical excision as possible. In nearly all cases, the ossicular chain must be included if recurrences are to be avoided. Due to the anatomic site of involvement, facial nerve paralysis and/or paresthesias may be seen or develop; this is probably due to mass effect rather than nerve invasion. In a few cases, reconstructive surgery may be required. Since this is a benign tumor, no radiation is required. Patients experience an excellent long term outcome, although recurrences can be seen (up to 15%), especially if the ossicular chain is not removed. Although controversial, metastases are not seen in this tumor. There are reports of disease in the neck lymph nodes, but these patients have also had other diseases or multiple surgeries, such that it may represent iatrogenic disease.

Hemangiopericytoma located in the cerebral cavity is an aggressive tumor of the Mesenchyme with oval nuclei with scant cytoplasm. "There is dense intercellular reticulin staining. Tumor cells can be fibroblastic, myxoid, or pericytic. These tumors, in contrast to meningiomas, do not stain with epithelial membrane antigen. They have a grade 2 or 3 biological behavior, and need to be distinguished from benign meningiomas because of their high rate of recurrence (68.2%) and metastases (Maier et al. 1992; Kleihues et al. 1993 )."

Malignant meningioma is a rare, fast-growing tumor that forms in one of the inner layers of the meninges (thin layers of tissue that cover and protect the brain and spinal cord). Malignant meningioma often spreads to other areas of the body.

The World Health Organization classification system defines both grade II and grade III meningiomas as malignant. Historically, histological subtypes have also been used in classification including:

- clear cell (WHO grade II),

- chordoid (WHO grade II),

- rhabdoid (WHO grade III), and

- papillary (WHO grade III)

Benign or low grade meningiomas (WHO grade I) include meningothelial, fibrous, transitional, psammomatous, angiomatous, microcystic, secretory, lymphoplasmacyte-rich, and metaplastic.

IIAs are uncommon, accounting for 2.6% to 6% of all intracranial aneurysms in autopsy studies.

Computed tomography (CT scan): A CT scan may be normal if it is done soon after the onset of symptoms. A CT scan is the best test to look for bleeding in or around your brain. In some hospitals, a perfusion CT scan may be done to see where the blood is flowing and not flowing in your brain.

Magnetic resonance imaging (MRI scan): A special MRI technique (diffusion MRI) may show evidence of an ischemic stroke within minutes of symptom onset. In some hospitals, a perfusion MRI scan may be done to see where the blood is flowing and not flowing in your brain.

Angiogram: a test that looks at the blood vessels that feed the brain. An angiogram will show whether the blood vessel is blocked by a clot, the blood vessel is narrowed, or if there is an abnormality of a blood vessel known as an aneurysm.

Carotid duplex: A carotid duplex is an ultrasound study that assesses whether or not you have atherosclerosis (narrowing) of the carotid arteries. These arteries are the large blood vessels in your neck that feed your brain.

Transcranial Doppler (TCD): Transcranial Doppler is an ultrasound study that assesses whether or not you have atherosclerosis (narrowing) of the blood vessels inside of your brain. It can also be used to see if you have emboli (blood clots) in your blood vessels.