Wiebers DO, Whisnant JP, Huston J III, et al. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet. 2003;362(9378):103–110.
Treatment of cerebral aneurysms
Treatment of symptomatic aneurysms before rupture is ideal. Supportive treatment to stabilize the patient includes efforts to lower intracranial pressure through hyperventilation or administration of mannitol, treatment of cerebral vasospasm with calcium channel blockers and blood volume expansion, and control of blood pressure.
The definitive treatment is surgical clipping of the aneurysm, but intravascular techniques such as coil embolization or stent placement are replacing clipping as the preferred treatment of many aneurysms, depending on size, location, and aneurysm anatomy. When aneurysm clipping is technically impossible, ligation of the feeding artery or carotid artery or wrapping of the aneurysm wall is sometimes necessary.
Arterial Dissection
Dissections may develop in the internal carotid artery or in any of its branches, as well as in the vertebral and basilar arteries. Dissection may arise either extracranially or intracranially and can be of traumatic or spontaneous origin.
Clinical presentation of arterial dissection
The clinical features of dissection are variable. Patients may incur stroke, which typically occurs within the first 30 days of the dissection. The most common presentation of internal carotid artery dissection is headache with ipsilateral ophthalmic signs and contralateral neurologic deficits (see Chapter 10, Fig 10-4). The headache is usually located on the ipsilateral forehead, around the orbit, or in the neck. A bruit may be present. Sometimes symptoms of arterial dissection are delayed for weeks or months after trauma. Transient or permanent neurologic symptoms and signs include amaurosis fugax, acute stroke, monocular blindness, and ipsilateral Horner syndrome (Fig 10-4). If the dissection extends to the intracranial carotid segment, cranial neuropathies can occur, producing diplopia, dysgeusia, tongue paralysis, or facial numbness.
The vision loss associated with carotid dissection may be a result of embolic occlusion of the ophthalmic artery, central retinal artery, short posterior ciliary arteries, or retinal branch arteries. Alternatively, ophthalmic artery occlusion may be caused by the dissection itself. Reduced blood flow from carotid dissection is a rare cause of ocular ischemic syndrome.
Forty percent of dissections affect the vertebral and basilar arteries. General features of these dissections are headache, neck pain, and signs of brainstem and cerebellar dysfunction. Ocular motor cranial nerve palsies are common, and the consequences may progress to include quadriplegia, coma, and death.
Biousse V, Touboul PJ, D’Anglejan-Chatillon J, Lévy C, Schaison M, Bousser MG. Ophthalmologic manifestations of internal carotid artery dissection. Am J Ophthalmol. 1998;126(4):565–577.
Diagnosis of arterial dissection
An MRI scan is the diagnostic test of choice for extracranial carotid artery dissection. Routine MRI scanning shows a false lumen or an area of clotting in the cervical portion of the carotid artery (“crescent moon” sign; see Fig 10-4) and may identify areas of brain infarction. CT angiography or
MRI/MRA has a sensitivity of 87%–100%, and CT angiography has the added benefit of allowing visualization of the vertebrobasilar system. Digital subtraction angiography may also be used for diagnosis. Ultrasonography is not sufficient to detect a carotid dissection and can elicit a falsenegative result in nearly one-third of cases.
Treatment of arterial dissection
The treatment of arterial dissection is controversial, depending on the extent and location of the dissection and the patient’s overall condition. Treatment for extracranial carotid artery dissections may include medical therapy using antiplatelet drugs or anticoagulants, endovascular therapy with stent placement, and surgery with bypass procedures. Vertebrobasilar dissections cannot be approached surgically, but bypass procedures are sometimes employed.
Beletsky V, Nadareishvili Z, Lynch J, Shuaib A, Woolfenden A, Norris JW; Canadian Stroke Consortium. Cervical arterial dissection: time for a therapeutic clinical trial? Stroke. 2003;34(12):2856–2860.
Arteriovenous Malformations
Like aneurysms, AVMs are usually congenital and may be familial. Symptoms typically arise before 30 years of age, with a slight male preponderance, and 6% of patients also have an intracranial aneurysm. Intracranial hemorrhage with or without subarachnoid hemorrhage is the initial presentation in half of the cases. In contrast to patients with saccular aneurysms, patients with AVMs are much more likely to become symptomatic before a hemorrhage occurs (Fig 14-17). Seizures are the first manifestation in 30% of affected patients, whereas 20% have headaches or other focal neurologic deficits initially. The neurologic symptoms may be progressive or transient.
Figure 14-17 A, This 24-year-old man was referred with a 2- to 3-year history of prominent blood vessels in the right eye. Visual acuity was 20/20 bilaterally, but visual fields (B, C) demonstrated a left homonymous hemianopia. D, A T2-weighted MRI scan demonstrated a large right basal ganglia arteriovenous malformation (AVM) (red arrow). E, Angiogram of the right internal carotid artery confirmed the basal ganglia AVM (arrow). (Courtesy of Steven A. Newman, MD.)
Of the 90% of AVMs that are supratentorial, about 70% are cortical and 20% are deep. The remaining 10% are located in the posterior fossa or dura mater. Early mortality occurs in up to 20% of cases when bleeding takes place, and the rebleeding rate is 2.5% each year. Most AVMs bleed into the brain, causing headaches and focal neurologic deficits.
The neuro-ophthalmic manifestations of an AVM depend on its location. Cortical AVMs in the occipital lobe may produce visual symptoms and headaches that resemble migraine. The visual phenomena are usually brief and unformed; typical migrainous scintillating scotomata may occur but are rare (see Chapter 12, Fig 12-1). Hemispheric AVMs may produce homonymous visual field defects. Signs and symptoms of brainstem AVMs are not specific and may include diplopia, nystagmus, dizziness, ocular motor nerve palsy, gaze palsy, anisocoria, or pupillary light–near dissociation. Reports of transient monocular visual loss caused by a steal phenomenon from an intracranial AVM are rare.
Some patients with AVMs report a subjective intracranial bruit, and occasionally the examiner will detect a bruit with auscultation of the skull over the AVM.
Abnormal arterial communication with one of the dural venous sinuses (dural AVM) results in elevated venous pressure and in turn increased intracranial pressure. Dural AVMs account for 10%– 15% of intracranial AVMs. Patients often have tinnitus and an audible bruit in addition to signs and symptoms of increased intracranial pressure. Dural AVMs are difficult to diagnose without catheter angiography and may be mistaken for typical idiopathic intracranial hypertension (IIH) (see Chapter 4). Dural AVMs should be considered in the patient who does not fit the usual IIH demographics and who has no other demonstrable cause of increased intracranial pressure.
Diagnosis of arteriovenous malformations
If bleeding is suspected, an unenhanced CT scan will show the hemorrhage. Although unruptured AVMs are typically apparent on an enhanced CT scan, MRI scanning is more sensitive for visualizing small AVMs. MRI demonstrates the heterogeneous signals representing the various elements of the lesion: blood vessels, brain, flowing and clotted blood, calcium, hemorrhage, or edema. Calcified AVMs are sometimes identifiable on plain radiograph or CT scan. Cerebral angiography is required to show the anatomy clearly and to define the feeding and draining vessels of the AVM.
Treatment of arteriovenous malformations
The location of the AVM, the anatomy of the feeding and draining vessels, and the size of the lesion all affect the choice of treatment. The treatment modalities of surgical resection, ligation of feeding vessels, embolization, and stereotactic radiosurgery can be used alone or in combination. Seizures usually improve with anticonvulsant therapy.
Kupersmith MJ, Vargas ME, Yashar A, et al. Occipital arteriovenous malformations: visual disturbances and presentation. Neurology. 1996;46(4):953–957.