Neither the pathogenesis nor the natural history of brain arteriovenous malformations (BAVMs) and dural arteriovenous fistulas (DAVFs) has as yet been fully elucidated. BAVMs are generally considered to be congenital vascular disorders, while some factors after birth may still influence their genesis or growth. Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia characterized by dilated vessels and AVMs, and is also known as a genetic disease associated with BAVMs. Three genes, endoglin, ALK-1 and SMAD-4 are associated with HHT. The natural history of BAVMs is influenced by angioarchitecture and prior hemorrhage. DAVFs are considered as an acquired lesions ; however, their pathogenesis is not clear. The natural history of DAVFs is influenced by not only by the lesion's angioarchitecture such as its cortical venous drainage, but also by the patient's symptomatology. Furthermore DAVF can alter its angioarchitecture with proliferative changes in the arterial component and occlusive changes in venous drainage.
Despite the recent advances in endovascular technique and stereotactic radiosurgery, microsurgery still remains an important treatment option for complex brain arteriovenous malformations (bAVMs) and dural arteriovenous fistulas (dAVFs). This article describes the surgical strategy and tactics for shunt point extirpation used for each entity. In bAVM surgery, the shunt point (nidus) is approached from the arterial side and staged shunt reduction followed by total extirpation is achieved by feeder disconnection and nidus removal. Conversely, a venous approach is used and targeted shunt extirpation is proposed simultaneously in dAVF surgery, using selective cortical drainer disconnection. This strategy can achieve total elimination of the arteriovenous shunt in patients with Borden type III dAVF, and deaden critical cortical venous reflux in patients with Borden type II dAVF. The importance of understanding the difference in surgical strategies used between bAVM and dAVF surgery is discussed.
Endovascular treatments for arteriovenous shunts include transarterial embolization (TAE) and transvenous embolization (TVE) with solid materials such as coils or liquid materials such as NBCA and Onyx. For brain arterivenous malformations (BAVM), occlusion of the draining vein may cause bleeding due to the rupture of the nidus. Curative embolization requires total occlusion of the feeding arteries and the whole nidus, and is rarely accomplished except for small BAVM. Then TAE for feeders or the nidus with coils or liquid materials are performed as adjunctive treatments for surgical removal or stereotaxic radiosurgery. For dural arteriovenous fistulae (DAVF), occlusion of the affected sinus or draining vein cures the DAVF without bleeding. Therefore, TVE with coils or TAE with liquid materials are the primary treatments for DAVF.
The roles of stereotactic radiosurgery (SRS) for cerebral arteriovenous malformation (AVM) and intracranial dural arteriovenous fistula (AVF) are reviewed. Good indications for SRS to treat AVM are lesions that are small and deep-seated. The target is precisely covered with the prescription doses. The optimal prescription dose appeared to be 20 Gy. Our retrospective review of 321 AVM cases treated with gamma knife (GK) revealed approximately 80% of cases showed complete nidus obliteration on angiography 4 years after GK treatment. For AVM with a high risk of latency-period bleeding with angio-architectural structures such as a large volume, high flow shunt, extracranial arterial blood supply and intra-nidus aneurysm, we have been endeavoring to embolize the target. However, we noted transient radiation-induced edema in about 40% of cases, bleeding during the latency period in 5% and delayed radiation injury in 10%. Delayed radiation injuries included radiation necrosis, cyst formation, and chronic encapsulated hematoma. On the contrary, the indications for SRS to treat AVF are generally limited to residual shunting after interventional treatment. The AVF target is divided into the two types, one involving the only shunt point and the other the entire involved sinus or dura. AVF treated with SRS tend to show earlier obliteration than AVM without serious delayed radiation injury.
Patients showing stroke suggestive symptoms are directly referred to us through a “Neurosurgery Hotline”, in addition to head injuries and seizures without bothering duty doctors. We reviewed this referral system and report here the prevalence and clinical features of the patients. The hotline received emergency calls during off-hours between 5 : 30 PM and 8 : 45 AM including weekend and holiday hours. All 546 registered cases during the last 3 years (June 2009 to May 2012) were retrospectively reviewed. The 546 patients consisted of 285 male (mean 61.2 years old) and 261 female (68.9 years old) with an overall mean 65.0 years. Some 372 patients (68%) were referred to us properly as neurosurgical patients. Half of these (207 cases) were stroke patients. In total, 355 patients were admitted (262 of 331 ambulance and 92 of 215 walk-in cases). The concordance rates of initial symptoms with an exact stroke (49.9% overall accuracy) was high in speech disturbance (82.1%), paralysis (80.2%), and coma (77.4%) (Odds ratio : 95% confidence interval=5.78 : 3.26-10.24, 5.11 : 1.96-13.2, 3.78 : 1.7-8.38, respectively) but low in headache (23.6%), dizziness/vertigo (12.1%) and faintness/syncope ; (11.1%) (OR : 95%CI=0.21 : 0.12-0.34, 0.12 : 0.043-0.34, 0.12 : 0.02-0.76, respectively). Benign paroxysmal positional vertigo (26), hypertension (22), inflammatory disease (22) and hypoglycemia (10) were representative stroke mimics. The shortage of physicians and/or stroke-familiar doctors in rural areas has been a nationwide concern in Japan. In this situation, some neurosurgeons have taken the burden and responsibility upon themselves to triage neurosurgical diseases including stroke presenting with diverse clinical symptoms. Our hotline system worked well as a broad stroke triage.
The authors evaluated 75 patients who underwent reoperation for lumbar canal stenosis between 2003 and 2011. Both the causes for reoperation and the complications were reviewed. The causes for reoperation were also compared among the first surgical procedures. Symptoms and scores, such as the Japanese Orthopaedic Association (JOA) score and Visual Analog Scale (VAS) of back pain, were assessed preoperatively and postoperatively. Restenosis accounted for 30% of the reoperations. The reoperation rate did not differ among the first surgical procedures. An additional fixation procedure was conducted in five patients who underwent bilateral fenestration. Adjacent level stenosis tended to occur in the fixation group more than in pure decompression group. Complications were noticed in 10 patients : dural lacerations in 9 patients and a deep-seated infection in one patient. In the elderly patient group, improvement in JOA score was worse than in the younger-aged group. It is important to understand the causes or features of reoperation in order to improve treatment outcome.
Vertex epidural hematoma (EDH), which is an unusual consequence of head trauma, is characterized with manifold clinical course, so that the treatment strategy is still controversial. We describe three cases of vertex EDH with different clinical course. The first case was surgically treated because of slowly progressive neurological deterioration. The second case showed rapid improvement with spontaneous hematoma wash out. The third case was treated conservatively because of the absence of clinical symptoms despite compression of the superior sagittal sinus. Although several cases have been reported, clinical study with large number of cases is not available. Our cases showed typical but characteristic time courses, and hopefully they recall the further clinical interest to gain better understanding of the natural course of vertex EDH. The clinical course of patients with vertex EDH should be carefully observed to determine the appropriate timing of surgery.