Intracranial dissecting aneurysms in childhood

Traumatic posterior cerebral artery dissection and dissecting aneurysms: A systematic review with an illustrative case report

BACKGROUND

Traumatic posterior cerebral artery (tPCA) dissection and dissecting aneurysms are rare and constitute a challenging clinical entity.

OBJECTIVE

We analyze existing literature on tPCA dissection and present our institutional experience.

METHODS

We retrospectively queried our database for tPCA isolated dissection or dissecting aneurysms from 2008 until now and conducted a systematic literature review of published cases. We analyzed the clinical and radiographic characteristics and treatment outcomes of tPCA dissection.

RESULTS

Including our case, a total of 11 cases with either isolated dissection (n = 2) or dissecting aneurysms (n = 9) were included. The median age was 27 years, and 45% were females. The median interval between trauma and tPCA dissection diagnosis was nine days. Mental status declined in four (36%) patients. Half of the patients demonstrated tentorial subdural hematoma on head CT. Ischemic stroke was detected in three (43%) patients. Four (36%) patients were conservatively managed, one (9.1%) patient was treated with surgical clipping of the proximal PCA, and six patients underwent endovascular treatments. The complication rate was 20%. Immediate total occlusion was demonstrated in five patients (100%), and the conservatively managed case showed immediate, spontaneous thrombosis of the aneurysm. Glasgow Coma Scale scores were 15 in eight (89%) and 14 in one (11%) patients at the last clinical follow-up with a median of six months. The mortality and retreatment rates were null.

CONCLUSIONS

tPCA dissection is diagnosed late and commonly affects the young population. The clinical outcome for this condition is typically favorable. Current endovascular techniques showed considerable efficacy and safety.

Treatment for Spontaneous Intracranial Dissecting Aneurysms in Childhood: A Retrospective Study of 26 Cases

OBJECTIVE

This study aimed to assess the clinicoradiological features and treatment outcomes of intracranial dissecting aneurysms (IDAs) in childhood.

METHODS

We conducted a retrospective study of pediatric patients who were treated for spontaneous IDAs in our institute between January 2010 and December 2015. The clinical presentation, aneurysm characteristics, treatment modality, and outcome were studied.

RESULTS

We studied 26 pediatric patients (mean age, 13.4 years; range, 4-18 years) with 31 IDAs who comprised 6.9% of all IDA patients treated during the same period. Seventeen (65.4%) patients were males, and nine (34.6%) were females. The incidence of large (≥10 mm in size) or giant aneurysms (≥25 mm in size) was 65.5%. Twenty-one (80.8%) patients underwent endovascular or surgical treatment and five (19.2%) received conservative treatment. Perioperative complications occurred in three patients, in whom two eventually recovered completely with a Glasgow Outcome Scale (GOS) score of 5 and one partially recovered with a GOS score 4. Overall, 25 (96.2%) patients had a favorable outcome and one (3.8%) had an unfavorable outcome at a mean follow-up of 22.8 months (range, 6-60 months).

CONCLUSION

Pediatric IDAs are rare. In this series, endovascular management was a relatively safe and effective method of treatment for pediatric IDAs. However, continued follow-up is required because of the possibility of aneurysm recurrence and de novo aneurysm formation after treatment.

Cerebral dissecting aneurysms in patients with essential thrombocythemia

The etiologies of intracranial artery dissection are various, the exogenous as well as inherited connective tissue disorders. We report on a patient who presented with diffuse subarachnoid hemorrhage who had been suffered from essential thrombocythemia. He was diagnosed to multiple dissecting aneurysms of left superior cerebellar artery, left posterior inferior cerebellar artery and right pericallosal artery and treated with endovascular coil embolization.

Fatal ischemic stroke due to dissecting aneurysm of the intracranial arteries presenting as sudden unexpected death in childhood

Sudden unexpected death is any nontraumatic death in healthy individuals with normal activities for age until acute demise. Whereas not uncommon in adults and infants, it is considered a rarity in children, with most cases due to infection or occult cardiovascular abnormalities. Pathologic intracranial findings are rarely found in sudden unexpected death in childhood, with most cases due to occult intracranial neoplasms. Cerebral arterial dissection is an uncommon cause of arterial ischemic stroke in childhood. Outcome is poor, with more than 20% of patients dying. We report 4 cases of sudden unexpected death due to arterial ischemic stroke after cerebral arterial dissection in childhood and present a review of the literature.

Ruptured dissecting cerebral aneurysms in young people: report of three cases

Intracranial arterial aneurysms in the pediatric population are rare. Among these, dissecting aneurysms are the most frequent, followed by saccular, infectious, and posttraumatic. It is widely known that aneurysmal rupture is uncommon in the first two decades of life. Spontaneous dissecting aneurysms (SDAs) of the middle cerebral artery (MCA) affecting young individuals most frequently present as occlusive syndrome with ischemia, although bleeding and subarachnoid hemorrhage can also occur. Between March 2006 and January 2008, three young patients (20 months, 8 and 20 years old) were surgically treated for MCA SDA in the Neurosurgical Department of "12 de Octubre" Hospital of Madrid. These patients showed hemorrhage as primary radiological finding, and all of them underwent surgical operation. Aneurysms were always treated by trapping, with aneurysmectomy in one case, but no distal extra-intracranial (EC-IC) bypass was performed. In two cases, the histological examination of the aneurysm's wall evidenced signs of subintimal dissection with widespread disruption of the internal elastic lamina and media with neointima formation and intramural hemorrhage. Although bleeding is an uncommon presenting sign of SDAs, they should be suspected in young people showing hemorrhage at CT scan. Early surgical treatment and, if possible, preoperative neuroimaging evaluation of intracranial vessels should be performed to reduce the mortality in these patients despite a higher postoperative morbidity. From a technical point of view, surgical trapping of the aneurysm seems to be a reasonable treatment strategy especially in an emergency basis. However, whenever possible, an EC-IC bypass could help diminish the ischemic morbidity associated with these aneurysms.

Paediatric dissecting posterior cerebral aneurysms: report of two cases and review of the literature

INTRODUCTION

Intracranial aneurysms in the paediatric population are uncommon, accounting for 2% to 6% of all aneurysms, and spontaneous arterial dissection is rarely reported as the cause of aneurysms in children, especially in the posterior cerebral artery.

METHODS

Two cases of paediatric spontaneous posterior cerebral artery dissecting aneurysms are reported, one in a 33-month-old male child presenting with aneurysmal rupture and subarachnoid haemorrhage and the other in a 9-year-old boy with an unruptured aneurysm.

RESULTS

The first child was successfully treated by endovascular parent vessel occlusion without neurological deficit and in the second a spontaneous thrombosis of the aneurysm and its parent artery occurred associated with hydrocephalus and a favourable outcome.

CONCLUSION

Dissecting aneurysms are dynamic lesions with variable and unpredictable evolution and close follow-up and/or early treatment is warranted. Spontaneous arterial dissection is a rare, probably still under-recognized, cause of intracranial aneurysms that may be responsible for a significant number of aneurysms and spontaneous aneurysmal thromboses in children.

Clinical analysis of vertebrobasilar dissection

BACKGROUND

The natural history of vertebrobasilar artery dissection (VAD) is not fully known. The purpose of this study was to review the clinical outcome of the patients with VAD, then to propose an appropriate management strategy for VAD.

METHOD

From 1992 to 2004, 35 VAD patients admitted to our institutes were retrospectively reviewed. There were 28 men and 7 women, whose age ranged from 4 to 67 years with a mean age of 44 years. Angiography was assessed to document the shape, and location of the dissecting aneurysm with respect to the posterior inferior cerebellar artery (PICA). A modified Rankin score was assigned for functional outcome. The functional outcome scores were analyzed according to the patient's age, gender, hypertension history, the pattern of initial manifestation, angiographic shape of VAD, angiographic location of VAD, treatment modality.

FINDINGS

There was no statistically significant difference between the functional outcome with age, gender, trauma history and past medical history of hypertension. Of 35 patients, 22 presented with SAH, 11 with ischemic symptoms and 2 were incidentally detected. The patients without SAH had a better functional outcome than those with SAH (p = 0.029). There was statistical significance between Hunt-Hess (H-H) grade and clinical outcome (p = 0.032). The shape and location of VAD was not significantly related to the functional outcome (p = 0.294, 0.840). But all the cases of rebleeding and mortality (except one case with initially poor H-H grade) developed exclusively in patients with aneurysms. There was no statistically significant correlation between the treatment modality and the outcome (p = 0.691).

CONCLUSION

The VAD patients with SAH would be recommended to be managed by either surgical or endovascular treatment, but those without SAH, could be managed conservatively with antiplatelet therapy and/or anticoagulation.

Craniocervical arterial dissection in children: clinical and radiographic presentation and outcome

Craniocervical arterial dissection is a recognized cause of arterial ischemic stroke in children. Whether children with craniocervical arterial dissection have dissection characteristics different from those of adults is unclear. A retrospective review of children, 1 month to 18 years of age, with dissection from two Canadian pediatric ischemic stroke registry centers was conducted. From 213 patients with arterial ischemic stroke, 16 (7.5%) were identified with dissection, 37.5% had warning symptoms, and 50% had a history of head or neck trauma. The clinical presentation included headache (44%), altered consciousness (25%), seizures (12.5%), and focal deficits (87.5%). Dissection involved extracranial vessels in 75% and anterior circulation in 56%. Follow-up included complete recovery in 43%, mild to moderate deficits in 44%, and severe deficits in 13%. Fourteen (87.5%) children received antithrombotic treatment. Follow-up angiography showed resolution of abnormalities in 60% of vessels. Total occlusion had the worst outcome for recanalization. In conclusion, the etiology of arterial dissection in the majority of children appears to be either trauma or idiopathic. Long-term angiography shows variable outcomes, depending on the initial findings. The relationship of angiographic outcomes with recurrent strokes requires further study in pediatric dissection. (J Child Neurol 2006;21:8-16).

Clinically occult chronic dissecting aneurysm of the superior cerebellar artery in a child

An isolated chronic dissecting aneurysm of the left superior cerebellar artery was discovered incidentally in a 12-year-old girl. There was no history of any previous trauma or witnessed abnormal neurological incident at any stage during her life. She was and has since remained asymptomatic and the aneurysm has remained radiologically stable for over 3 years. A conservative approach to the management of such incidental asymptomatic lesions is thus suggested.

Middle cerebral artery dissections: Differences between isolated and extended dissections of internal carotid artery

Isolated middle cerebral artery dissection (MCAD) has rarely been encountered clinically and few have reviewed it systemically. The etiologies, clinical manifestations, natural clinical course and prognosis of MCAD remain poorly understood. From 1995 to 2004, there were 5 cases diagnosed clinically and angiographically to have MCAD (isolated MCAD in 1, ICAD-MCAD in 4) from a medical center in Taiwan. MEDLINE (1966-2003) was searched for published articles in English that concerned the diagnosis of MCAD. Clinical presentations, stroke types, angiographic findings, etiologies, treatment strategies and outcomes were compared between cases with isolated MCAD or ICAD-MCAD. There were 23 cases (male, 46%; mean age, 22.9+/-19.5 years) with 24 events of isolated MCAD and 31 cases (male, 47%; mean age, 22.2+/-12.9 years) with 35 events of ICAD-MCAD. The types of stroke in isolated MCAD group included subarachnoid hemorrhage (12%) and cerebral infarction (88%); and in ICAD-MCAD group were subarachnoid hemorrhage (6%) and cerebral infarction (94%). The presenting symptoms were similar between both groups. Fluctuating course was more often in isolated MCAD than in ICAD-MCAD (17% vs. 3%, p=0.061). Recurrence of dissection events in both groups was infrequent (4% vs. 9%, p=0.56). Both groups had high case-fatality rates (MCAD, 48%; ICAD-MCAD, 58%). The cause of dissection in both groups was idiopathic in the majority. Congenital vessel wall defects were found in 26% of ICAD-MCAD, but in only 4% of isolated MCAD (p=0.066). In contrast, preceded trauma was more often found in isolated MCAD than ICAD-MCAD (35% vs. 19%, p=0.085). Arteritis was noted in 16% of ICAD-MCAD patients, but none in isolated MCAD. Angiography revealed segmental stenosis in 72% of isolated MCAD and 96% of ICAD-MCAD. Aneurysmal dilatation of the involved cerebral arteries was noted in 28% of isolated MCAD, but none in MCAD-ICAD. Both isolated MCAD and ICAD-MCAD can cause vascular events with high mortality rates. Several aspects differed between 2 groups, including clinical course, underlying etiologies and angiographic findings.

Fatal bleeding from arterial dissection after clipping of a ruptured aneurysm--case report

A 67-year-old man died of subarachnoid hemorrhage (SAH) resulting from dissection of the distal part of the anterior cerebral artery (ACA). A saccular aneurysm in the anterior communicating artery had ruptured and was successfully clipped on Day 0. The patient recovered consciousness after surgery but his condition deteriorated due to another SAH on Day 1. A second surgical procedure disclosed bleeding from a laceration in the opposite wall of the ACA distal to the clipped aneurysm. Histological examination of the autopsy specimens revealed damage to the internal elastic lamina and inflammatory infiltration of leukocytes. The fatal dissection may have resulted from atherosclerosis, hemodynamic stress caused by hypertension, or trauma due to surgical manipulation.

Histological Study of the Normal Vertebral Artery-Etiology of Dissecting Aneurysms-

Histological evaluation of dissecting aneurysms of the cerebral arteries has suggested that defects in the internal elastic lamina (IEL) induce dissection of the arterial wall. Dissecting aneurysms occur most frequently in the vertebral artery (VA). The present study examined sections of the normal VA to elucidate the mechanisms of arterial dissection. Bilateral VAs (20 vessels) were obtained from 10 patients who died of causes other than intracranial lesions. The VAs were detached from the VA union to the site 10 mm proximal from the point penetrating the dura mater. The VAs were cut at 5-mm intervals, and each segment was observed using modified Masson's trichrome staining for elastic fibers. The thickness of the media and adventitia significantly thinned after the origin of the posterior inferior cerebellar artery (PICA). IEL defects were observed at 35 sites in 11 vessels from six subjects. There was a high incidence of IEL defects in the extradural portion and near the origin of the PICA, areas frequently involved in arterial dissection. There was a high incidence of intimal thinning at areas of IEL defects (19 of 35), and thinning was particularly marked distal to the origin of the PICA. In the absence of intimal thickening, the vascular strength at the site of IEL defects may be reduced, which would promote the occurrence and progression of arterial dissection.

Dissecting aneurysms of the middle cerebral artery: neuroradiological and clinical features

There are few reported cases of nontraumatic dissecting aneurysms of the middle cerebral artery (MCA), and their neuroradiological and clinical features have not been analysed. We looked at these aspects in a collaborative study. We reviewed 13 patients diagnosed as having a dissecting aneurysm of the MCA based on clinical signs and neuroradiological findings in 46 stroke centres between 1995 and 1999. There were four patients who presented with cerebral ischaemia, and nine who presented with bleeding. Of the former group, three were aged less than 15 years. Cerebral angiography showed extensive stenosis and a double lumen of the M1 portion in all four patients. High signal on T1-weighted images around the arterial flow void, due to intramural haematoma, was often seen in the second week. MR angiography showed findings corresponding those of intra-arterial angiography in all four cases. We saw an infarct on CT or MRI in territory of the perforating branches of the M1 segment in all four patients. In the patients presenting with bleeding, pure subarachnoid haemorrhage or a sylvian fissure haematoma was seen on initial CT, and the predominant angiographic finding was dilatation with stenosis, but the site of the lesions was not uniform. A double lumen or intimal flap was seen in about half the cases. Rebleeding occurred within 14 days of the onset in five of the nine patients, with a poor prognosis.

Traumatic posterior cerebral artery occlusion in a 14-month-old child

Following a head injury, a 14-month-old male presented with neck stiffness and 24 hours later developed bilateral lateral rectus palsies. An unenhanced cerebral computed tomographic scan performed on admission revealed evidence of subarachnoid hemorrhage, cerebral edema, and mild-to-moderate compensated supratentorial hydrocephalus. A second scan performed 96 hours after the head injury revealed a mural thrombus at the tip of the basilar artery without any evidence of infarction. A third scan performed 12 days later revealed that the thrombus had resolved. However, a left posterior cerebral artery territory infarct was visualized. We postulate that the thrombus had embolized to the left posterior cerebral artery and caused occlusion of its cortical branch and subsequent infarction. A magnetic resonance angiography performed 20 days later excluded any vascular abnormality. The bilateral lateral rectus palsies persisted at the 6-month follow-up. To our knowledge, a head injury leading to a posterior cerebral artery territory infarct has not been reported earlier in a young child.

Dissection of the intracranial internal carotid artery producing isolated oculomotor nerve palsy with sparing of pupil

Dissection of the internal carotid artery usually occurs in the cervical segment, but rarely may involve the artery in the intracranial course (1). The clinical course of intracranial dissection is often catastrophic, with rapid onset of profound neurological deficit, as a result of middle and/or anterior cerebral artery involvement. When this occurs the mortality rate is generally considered high. We describe a case of intracranial internal carotid artery dissection following trivial trauma presented with an isolated painful pupillary sparing oculomotor nerve palsy.

Dissecting hematoma of intracranial internal carotid artery in an 8-year-old girl

BACKGROUND

An 8-year-old girl had a minor fall without head trauma and she collapsed the following day while playing. She was awake but mute with focal neurologic signs when admitted to hospital. Radiologic imaging studies showed a progressive left cerebral infarct with left hemisphere vascular narrowing and beading. She died on the third hospital day.

METHODS

Autopsy including exploration of neck vessels and neuropathological examination was performed. Postmortem studies included immunostaining for immunoglobulins and fixed complement.

RESULTS

Subtotal subintimal dissections of both proximal supraclinoid internal carotid arteries were found microscopically. On the left, the subintimal dissection extended into the major branches of the left internal carotid artery as dissecting hematomas with a major compromise of the arterial lumina. Specific IgM deposition at the dissection sites was found. A literature review shows that subintimal dissection of the intracranial internal carotid artery or its branches occurs rarely, it is often fatal, and it is present in patients with a mean age of 17.5 years in cases studied pathologically. Trauma and physical exertion are the most common associated factors.

CONCLUSIONS

Among the causes of ischemic stroke in young individuals, dissecting hematomas of the intracranial portions of the internal carotid artery system rank low. Few reported cases have identifiable pre-existing pathology. The pathogenesis of dissecting hematomas in this region is reviewed and expanded with speculation regarding relevant developmental, anatomical, flow stress and possibly humoral factors that are involved in the disruption of the arterial elastica and subsequent development and extension of a subintimal hematoma resulting in luminal closure and often death.

Cerebrovascular arterial dissection in children and young adults

Dissection of the cervical and intracranial portions of the carotid and vertebrobasilar arteries may occur spontaneously or in association with trauma or other underlying risk factors. Astute recognition allows appropriate diagnostic and therapeutic protocols to be instituted. Dissection of extracranial carotid and vertebral arteries differ from their intracranial counterparts, both in terms of presentation and prognosis. Limited data are available regarding the most effective medical treatment of dissection in children and young adults. Interventional neuroradiology may offer a new approach in difficult cases. A multicenter controlled clinical trial is needed to assess the most effective treatment.

Clinicopathological features of non-atherosclerotic cerebral arterial trunk aneurysms

Internal elastic lamina (IEL) is the most vital structure of the cerebral arterial wall. Longstanding weakness of the IEL due to hemodynamic stress is compensated by adaptive intimal thickening. Formation of cerebral arterial trunk aneurysm is assumed to be the result of a break in the equilibrium between hemodynamic stress and the condition of the IEL and intima. Cerebral arterial trunk aneurysms unrelated to the branching zones have several lesional patterns of IEL and the state of intima. There is a strong relationship between the pathological features of aneurysms and their clinical courses. We attempt to delineate the concept of cerebral arterial trunk aneurysms including 'dissecting aneurysms' and 'fusiform aneurysms'.

Traumatic intracranial aneurysms

Traumatic intracranial aneurysms are rare, occurring in fewer than 1% of patients with cerebral aneurysms. They can occur following blunt or penetrating head trauma and are more common in the pediatric population. Traumatic aneurysms can be categorized histologically as true, false, or mixed, with false aneurysms being the most common. These aneurysms can present in a variety of ways, but are typically associated with an acute episode of delayed intracranial hemorrhage with an average time from initial trauma to aneurysm hemorrhage of approximately 21 days. The mortality rate for patients harboring these aneurysms may be as high as 50%. Prompt diagnosis based on arteriography and aggressive surgical management are associated with better outcome than conservative treatment. The authors describe a classification scheme for traumatic aneurysms based on their anatomical location and conclude that 1) post-traumatic aneurysm must be considered in patients with acute neurological deterioration following closed head injury; 2) they can occur following mild closed head injury; 3) they occur more commonly in children than in adults; and 4) surgical clipping and/or endovascular occlusion is the definitive treatment.

Proposed classification of nonatherosclerotic cerebral fusiform and dissecting aneurysms

OBJECTIVE

The aim of this study is to classify nonatherosclerotic aneurysms unrelated to the branching zones (including fusiform aneurysms and dissecting aneurysms).

METHODS

Damage to the internal elastic lamina (IEL) is often an associated factor in the pathogenesis of aneurysm formation. In this study, 85 nonatherosclerotic aneurysms arising from an arterial trunk unrelated to the branching zones were classified into four different types, based on the lesional patterns of the IEL and the state of the intima. Type 1 corresponded to classic dissecting aneurysms, the pathogenesis of which was characterized by acute widespread disruption of the IEL without intimal thickening. Patients with Type 1 aneurysms had an ominous clinical course, and many presented with sudden subarachnoid hemorrhage with frequent rebleeding. Type 2 aneurysms were segmental ectasias, which had an extended and/or fragmented IEL with intimal thickening. Weakness of the arterial wall caused by the damaged IEL was assumed to be compensated by the intimal thickening. The luminal surface of the thickened intima was smooth without thrombus formation. The patients with Type 2 aneurysms had a placid clinical course. Type 3 aneurysms were dolichoectatic dissecting aneurysms, pathologically characterized by fragmentation of the IEL, multiple dissections of thickened intima, and organized thrombus in the lumen. Most of them were symptomatic and progressively enlarged over time. Type 4 aneurysms were saccular aneurysms unrelated to the branching zones. They arose in areas with minimally disrupted IEL without intimal thickening, and there was a risk of rupture.

CONCLUSION

There was a strong relationship between the pathological features of the aneurysms and their clinical courses. This classification may provide a rationale for modes of treatment.

Tissue plasminogen activator in a vertebral artery dissection

BACKGROUND

Spontaneous dissection of the vertebral artery is uncommon.

METHOD

Case study.

RESULTS

We report a 49-year-old woman who presented with the rapidly progressing basilar artery syndrome who was given an intravenous dose of tissue plasminogen activator seven hours after the onset of first symptoms. Thirty minutes after the injection, a dramatic recovery of the patient's consciousness and neurological signs was noted.

CONCLUSION

To our knowledge, this is the first reported case of intravenous tissue plasminogen activator use in acute vertebral artery dissection.

Nontraumatic intracranial internal carotid artery dissection: a case report

The case presented offers a demonstration of a rare yet devastating condition that may go unrecognized and incompletely worked up by the emergency physician. Internal carotid artery dissection is seen most often in previously healthy, young patients and thus all efforts toward diagnosing this condition and providing proper stabilization must be made. Unfortunately, little advancement in the therapeutic progress of this frequently fatal condition has been made over the past decades. To date, both medical management and surgical techniques have been utilized with variable success. This case should serve to remind physicians evaluating young patients with stroke symptoms or other neurological findings that a negative head CT scan may not be the last test necessary for the definitive diagnosis.

Middle cerebral artery dissecting aneurysm with persistent patent pseudolumen. Case report

The extremely rare condition of an ischemic right middle cerebral artery dissecting aneurysm with persistent patent pseudolumen is described. In the majority of cases of dissecting aneurysms, the pseudolumen persists for a very short time, probably because reentry from the pseudolumen is minimal or nonexistent. In contrast, the present case was assumed to have sufficient reentry from the bypass flow in the pseudolumen. Endothelial formation both in the true lumen and the pseudolumen was suggested as the possible mechanism of the stabilized double lumen.

Spontaneous extracranial carotid artery dissection in children

Dissection of cerebral arteries as a cause of stroke is rarely recognized in children. Two patients with stroke due to extracranial carotid artery dissection are reported. A 7-year-old girl with a 2-week history of right arm chorea had a left basal ganglia infarct and is receiving haloperidol for persistent chorea. The second patient, a 15-year-old boy, developed aphasia and right hemiparesis a day before admission during a football game without obvious trauma. He had a large left middle cerebral artery infarct and died of cerebral edema and herniation. We believe that strokes due to arterial dissection are more common than currently recognized, partly because of a lack of history of trauma, and suggest that cerebral artery dissection be considered as an etiology of childhood strokes. Greater awareness of arterial dissection as a cause of stroke and availability of noninvasive techniques like magnetic resonance angiography should result in a more accurate diagnosis and improved prognosis in these patients.

Benign arterial dissections of the posterior circulation

Four young adults with spontaneous dissection of the vertebrobasilar system are reported. Clinically, two patients presented with subarachnoid hemorrhage and two with brain-stem ischemia. In two cases of ruptured arterial dissection of the posterior cerebral artery, angiography demonstrated fusiform and "sausage-like" dilatation of the involved vessel. In two cases of occlusive dissection of the basilar artery, angiography revealed the typical "string sign." All four patients were treated conservatively: three survive in good clinical condition and one remains disabled. Follow-up angiograms showed spontaneous healing of the lesion with return to an almost normal arterial configuration in two cases; residual narrowing corresponding to the dissection was the most notable finding in the other two. It is recommended that, in a subset of neurologically stable patients, angiographic monitoring is undertaken to assess the tendency for spontaneous repair before surgical intervention is planned.

Growing intracranial arteriovenous malformation in a newborn

A case is reported of a growing arteriovenous malformation in a newborn, premature baby. The reason for early operative intervention is emphasized, based on histological investigation of the malformation. The literature is reviewed.

Fatal intracranial arterial dissection: clinical pathological correlation

The clinical pathological features of fatal arterial dissection confined to the intracranial vessels are described. Three patients with anterior circulation dissections presented with focal ischaemic neurological deficits and pathological examination of involved vessels revealed a dissection plane between internal elastic lamina and media accompanied by intravascular thrombosis. Three of four patients with posterior circulation dissections had clinical pathological features of subarachnoid haemorrhage and at necropsy had transmural dissections. In contrast to previous reports, primary vasculopathies either degenerative or inflammatory were not identified in affected vessels. The pathogenesis of intracranial arterial dissection is discussed and the clinical features are correlated with the pathological abnormalities.

Reticular fiber deficiency in the intracranial arteries of patients with dissecting aneurysm and review of the possible pathogenesis of previously reported cases

The pattern of reticular fibers in the tunica media of the major intracranial arteries was investigated in two patients with dissecting aneurysm. In numerous circumscribed areas, the reticular fibers were absent close to the internal elastic lamina in all major arteries of each patient. It is suggested that the subintimal deficiency in reticular fibers results in insufficient fixing of the tunica intima to the media contributing to their separation when the internal elastic lamina becomes defective. The presumed etiologies of the previously reported cases are reviewed and the possible origin of the deficiency in reticular fibers is discussed.

Intracranial dissecting aneurysms of the posterior circulation. Report of six cases and review of the literature

Dissecting aneurysms of the intracranial posterior circulation are unusual lesions that affect otherwise healthy young adults, are difficult to diagnose and manage, and carry a high morbidity and mortality rate. Headache in the suboccipital-posterior cervical region is the most common presenting symptom. The dissection usually occurs between the intima or internal elastic lamina and the media; subadventitial dissection does occur and accounts for the infrequent finding of subarachnoid hemorrhage. A deficit in the inner layers of the vessel is the proposed source of dissection. The angiographic features are inconsistent, although an irregularly narrowed arterial segment with proximal and/or distal dilatation are typical findings. Depending on the location of the dissection, the surgical options are: ligation, trapping, or reinforcement of exposed abnormal portions of the vessel. Anticoagulation therapy is not indicated in the management of this lesion.

Cerebral dissecting aneurysms in patients with moyamoya disease. Report of two cases

Dissecting intracranial arterial aneurysms were identified in a 16-year-old girl and a 48-year-old man with moyamoya disease. Hemiplegia or tetraplegia rapidly developed. Angiography revealed bilateral stenoses or occlusion of the bifurcation of the internal carotid arteries (ICA's) and an unusual vascular network at the base of the brain. Autopsy confirmed massive hemorrhage from the thalamus and putamen, with intraventricular extension. The intracranial segments of both ICA's were markedly stenotic in both patients, due to eccentric fibroelastic intimal thickening. In one patient, a dissecting aneurysm was identified microscopically, involving the proximal segment of the left anterior cerebral artery. In the other patient, the right middle cerebral artery (MCA) was dissected beneath the internal elastic lamina along the entire length of the horizontal segment of the MCA. Thus, cerebral dissecting aneurysms may be present in patients with moyamoya disease.