giovedì 18 maggio 2006

Sturge-Weber syndrome (SWS)


Plain films (Figure 1 and Figure 2) show “tram track” calcification in the right frontal region. The gyral or subcortical calcification is better seen in the CT image (Figure 3).
Axial T1 image (Figure 4) demonstrates volume loss in the right frontal area with thickened diploic space in this region. Sagittal SE image (Figure 5) shows multiple round signal voids, which are dilated deep medullary veins.
Postcontrast images (Figure 7 and Figure 8) show leptomeningeal enhancement, suggestive of increased venous collaterals and prominence of the right transmantle (transcerebral) veins (Figure 6). Also note the enlarged ipsilateral right choroid plexus (Figure 7).
GRE (Figure 7) shows “blooming” in the right frontal area corresponding to the area of calcification seen on CT.
MRV (Figure 9) findings demonstrate a hypoplastic right transverse sinus as well as a very small right-sided jugular vein.

Diagnosis: Sturge-Weber syndrome (SWS)

SWS, also known as encephalotrigeminal angiomatosis or meningiofacial angiomatosis, is a rare neurocutaneous syndrome that includes a facial port wine stain and associated leptomeningeal angiomatosis. The pial angiomatosis may be bilateral in 20% of cases.

It is generally considered nonhereditary. Embryologically, the abnormality most likely develops at gestational weeks four to eight. It is hypothesized that impaired venous outflow, caused by loss of normal connections between cortical veins and dural and calvarial circulation, results in persistent, primitive vascular plexus. This results in poor venous drainage from the cerebral cortex and progressive cortical damage.

Seizures often begin in the first year of life. It is the presenting feature in 80% of patients and may be generalized or partial. Hemiparesis may occur in up to 30% of cases resulting from hemiatrophy of brain. Developmental delay is common.

The port wine stain (nevus flammeus) usually occurs in the distribution of first and second division of trigeminal nerve. The choroid of eye may be involved with patients developing glaucoma.

The impaired venous drainage results in progressive ischemia of underlying brain and, eventually, progressive cortical atrophy and calcification. The cortical calcifications are rarely identified at birth. The most common area involved is the parieto-occipital region. Skull radiographs may show the typical “tram track” calcifications in apposing gyri. CT may also show enlargement of adjacent diploic space, hyperpneumatizaton of ipsilateral sinuses, and mastoid air cells.

MRI may show signs of ischemia and gliosis in early stages, but parenchymal atrophy over time. Gadolinium-enhanced MRI is highly sensitive to meningeal enhancement. Calcifications are better detected with gradient echo techniques. Enlargement of the ipsilateral choroid plexus may be secondary to hyperplasia or angiomatous involvement.

MR venogram may show enlarged deep collateral (medullary or subependymal) veins with lack of superficial cortical veins.

PET may show increased metabolism in early stages, which can be helpful in surgical planning.

martedì 9 maggio 2006



CT (Figure 1) and MR (Figure 2) imaging demonstrate the classic patterns of pachygyria, including:
- Smooth and markedly thickened cortex (Figure 1 and Figure 2)
- Broad, flat gyri with shallow sulci (focal or widespread)
- Vertically-oriented and shallow Sylvian fissures
- “Figure-of-eight” appearance of the brain on axial imaging

Diagnosis: Pachygyria

The findings in this case are consistent with pachygyria, which falls under the classification of an embryologic neuronal migration disorder. With pachygyria (synonymous with incomplete lissencephaly), there are focal areas of broad, flat gyri interrupted by a smooth and markedly thickened cortex. The etiology in some cases is linked to genetic abnormality, including mutations in chromosome 17 or Xq22, while others demonstrate no genetic abnormalities. Alternative etiologies for the development of this disorder include intrauterine insult (ischemic, metabolic, or viral such as CMV) during the 12th to 24th week of embryologic development. This results in damage to the germinal matrix and radial glial cells. Radial glial cells act as mechanical guides by which neurons are transported to the outer cortex during development. Damage to these cells results in subsequent malfunction of neuronal cell migration to the outer cortex.

Clinical findings

Onset and severity of symptoms varies, depending on the amount of cortical involvement. However, muscle spasms, hyperreflexia, refractory epilepsy, developmental delay, and mental retardation are common in children afflicted with the disorder.

Radiographic findings

Although CT is adequate in making the diagnosis, as in this case, MRI is more effective in evaluating and differentiating between neuronal migration disorders.

CT and MR imaging demonstrate the classic patterns of pachygyria, including:
- Smooth and markedly thickened cortex
- Broad, flat gyri with shallow sulci (focal or widespread)
- Vertically oriented and shallow Sylvian fissures
- “Figure-of-eight” appearance of the brain on axial imaging

venerdì 5 maggio 2006

Subarachnoid hemorrhage (SAH) due to left PICA aneurysm


High attenuation within basilar cisterns and subarachnoid spaces, extending to the Sylvian fissures consistent with hemorrhage. SAH was not seen to extend over the convexities (Figure 1, Figure 2 and Figure 3).
Vertebral artery injection digital subtraction angiography demonstrates an aneurysm of the Left PICA origin.
Figure 6 shows classic “teat” at site of rupture.

Differential diagnosis for subarachnoid hemorrhage (CT findings are diagnostic):
- Trauma
- Aneurysm rupture
- Angioma
- Neoplasm
- Cortical thrombosis
- Dissection from intraparenchymal hematoma

Differential diagnosis for cerebral aneurysm (angiographic findings are diagnostic)
DD for saccular aneurysms:
- Developmental/degenerative
- Traumatic pseudoaneurysm
- Mycotic
- Oncotic
- Flow related
- Vasculopathy related
- Drug related)

DD for fusiform aneurysms: Atherosclerosis

DD for dissecting aneurysms:
- Trauma
- Vasculopathy

Diagnosis: Subarachnoid hemorrhage (SAH) due to left PICA aneurysm

SAH is most commonly due to trauma. In the absence of trauma history or correlative findings, presence of SAH necessitates investigation for a cause. Nearly two thirds of these cases will be due to ruptured aneurysm. Clinically, patients experience severe headache. Patients often describe a “sentinel” headache, or prodrome indicating earlier bleeding. Less often, focal or global neurologic findings are present.

SAH is graded based on clinical presentation:
Grade 1) being mild headache
Grade 2) severe headache
Grade 3) mild mental status changes
Grade 4) obvious altered mental status or neurologic change
Grade 5) comatose or posturing

Long-term outcome directly correlates with grade at initial presentation. Of all patients with SAH, roughly 40% die within 24 hours and an additional 10% to 25% within six months. Of the survivors, half will have major long-term neurologic deficits.

Radiographically, high attenuation within subarachnoid spaces (sulci, ventricles, basal cisterns) on a noncontrast CT is the principal finding. Multidetector CT is up to 98% sensitive in the first 24 hours. Degree of SAH is also graded and has prognostic value, as does location of hemorrhage.

Complications of SAH include hydrocephalus, rebleeding, and vasospasm. Hydrocephalus is due to obstructing clot within the ventricular system and may be early or delayed. Early evidence is enlargement of the temporal horns. Rebleeding most often occurs within the first 24 hours, but can occur up to 2 weeks after initial insult. This is found in 20% to 30% of untreated patients and carries up to an 85% mortality. Vasospasm is the most feared complication, resulting in the greatest degree of morbidity and mortality, and affects nearly 40% of all patients. Peak time frame, according to the literature, is four to 12 days, although anecdotal experience from our institution suggests this is often seen earlier. Vasospasm can lead to ischemic events and progression of neurologic deficits.

As discussed, primary nontraumatic SAH is most commonly due to aneurysm rupture. Saccular aneurysms are true aneurysms and are the most common. These are thought to be congenital areas of weakening in arterial walls, which develop over many years into an aneurysm. Fusiform and dissecting are the other two major categories, and are much less common. Aneurysms have a fairly predictable distribution: 35% anterior communicating artery, 30% posterior communicating artery, 20% MCA bifurcation, and 15% vertebrobasilar system. Location of SAH is often a clue to aneurysm location. While no aneurysm is too small to exclude rupture, 4 to 7 mm appears to be the critical size. Aneurysms larger than 10 mm are at much higher risk. A patent aneurysm appears as an outpouching of contrast, while a thrombosed aneurysm may have a normal appearance. Lobulation or irregularity of aneurysm dome (“teat”) is an indication of possible rupture site, especially in the presence of multiple lesions.

Treatment of aneurysms has significantly progressed with intraarterial coil embolization. In the past, the only option was open surgical intervention. Timing of treatment is divided into two phases: early (within two to three days) and late (after ten to 14 days), avoiding the peak incidence of vasospasm. No significant outcome difference has been proven, however, proponents of early intervention for low-grade aneurysms cite the ability for aggressive treatment to lower risk of vasospasm once the aneurysm is controlled. Treatment for asymptomatic, unruptured aneurysms is even more controversial, due to postprocedural complications. Typically, lesions less than 5 mm are followed, while larger lesions are often treated.