**6. Diagnostic radiology**

Diagnosis can be established by invasive and semi-invasive radiological studies. At the bedside, transcranial Doppler (TCD) can detect stenosis of major arteries. Conventional CT or MRI helps to detect ischemic and hemorrhagic signs of MMD. CT angiography and conventional angiography are important to establish the exact point of narrowing in the circle of Willis.

*Moyamoya Disease: A Rare Vascular Disease of the CNS DOI: http://dx.doi.org/10.5772/intechopen.88770*


#### **Table 1.**

*Suzuki staging system for moyamoya.*

Suzuki and coworkers studied the angiographic progression of MMD and identified six stages (**Table 1**) of progression [1, 2].

This staging neither correlates with disease severity nor allows therapeutic risk stratification.

#### **6.1 CT head**

Cortical and/or subcortical infarction can be seen in the early stages, but in the later stages, dilatation of sulci or ventricles due to loss of volume can be seen. In a retrospective case series of 32 patients by Kim et al. [30], early stages (stages 1 and 2 of MMD) had mainly subcortical ischemic changes, whereas later stages (stage 3 and above) had cortical ischemic changes.

#### **6.2 Magnetic resonance imaging**

Diffusion and perfusion MR techniques are superior to CT scan for detection of subtle ischemic brain lesions especially in the acute condition. MRI was sensitive to detect watershed infarction in 50% of children as per a study done in Canada [31]. Dilated collateral vessels at the base of the brain are considered pathognomonic of MMD but seen only in some cases. In T2 sequences asymptomatic microbleeds may be seen. FLAIR images and T1 sequences may show a characteristic sign called ivy sign as in **Figure 2** (a linear pattern of increased signal in the leptomeninges and perivascular spaces) [33]. This is due to retrograde flow in leptomeninges resembling ivy creeping a stone. Magnetic resonance angiography (MRA) has surpassed conventional angiography in some centers as the primary imaging method although the latter is still considered as the gold standard.

#### **6.3 Angiography**

Conventional cerebral angiography is the gold standard for the diagnosis of MMD as it can clearly demonstrate the stenotic vessels in the anterior circulation as well as the collateral tuft of vessels formed (**Figure 3**). Apart from this, the small aneurysms which may be associated with MMD also can be detected in cerebral angiography.

**Figure 2.** *FLAIR sequence showing ivy sign (modified from [32]).*

**Figure 3.** *Characteristic "puff of smoke" appearance in cerebral angiography.*
