Those of the basilar artery and posterior cerebral artery are hard to reach surgically and are more accessible for endovascular management. These approaches are based on general experience, and the only randomized controlled trial directly comparing the different modalities was performed in relatively well people with small (less than 10 mm) aneurysms of the anterior cerebral artery and anterior communicating artery (together the "anterior circulation"), who constitute about 20 percent of all people with aneurysmal SAH. This trial, the International Subarachnoid Aneurysm Trial (ISAT), showed that in this group the likelihood of death or being dependent on others for activities of daily living was reduced (7.4 percent absolute risk reduction, 23.5 percent relative risk reduction) if endovascular coiling was used as opposed to surgery. The main drawback of coiling is the possibility that the aneurysm will recur; this risk is extremely small in the surgical approach. In ISAT, 8.3 percent needed further treatment in the longer term. Hence, people who have undergone coiling are typically followed up for many years afterwards with angiography or other measures to ensure recurrence of aneurysms is identified early. Other trials have also found a higher rate of recurrence necessitating further treatments. Vasospasm
Vasospasm, in which the blood vessels constrict and thus restrict blood flow, is a serious complication of SAH. It can cause ischemic brain injury (referred to as "delayed ischemia") and permanent brain damage due to lack of oxygen in parts of the brain. It can be fatal if severe.
Ossification of the posterior longitudinal ligament (OPLL) is a process of fibrosis, calcification, and ossification of the posterior longitudinal ligament of the spine, that may involve the spinal dura. Once considered a disorder unique to people of Asian heritage, it is now recognized as an uncommon disorder in a variety of patients with myelopathy. Causes
The causes of OPLL are unknown. However, genetic and environmental factors appear to play a role in pathogenesis. OPLL may also be associated with diffuse idiopathic skeletal hyperostosis

Diagnosis
Myeolography, including post-myelographic CT is likely the most effective imaging study an accurate diagnosis. Treatment
Surgical management options include extensive cervical laminectomy with or without an additional posterior arthrodesis, anterior decompression and arthrodesis, and posterior cervical laminoplasty. Treatment decisions can be made based on a grading systems devised by Hirabayashi et al., supplemented by the Nurick myelopathy classification system. Prognosis
Most patients suffer from only mild symptoms. Symptoms typically last approximately 13 months. Of patients without myelopathy at initial presentation, only 29% of them will develop myelopathy within 30 years. Epidemiology
The age range of patients with OPLL is from 32 to 81 years (mean = 53), with a male predominance. Prevalence is higher in those of Japanese or Asian ancestry (2-3.5%)  and rarer in other racial groups (0.16%). Schizophrenia patients in Japan may have as high as 20% incidence. References


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