**7.2 Computed tomography [CT]**

CT scan shows hyperdensities in basal ganglia, thalamus, ventricular system and subarachnoid spaces in the hemorrhagic type of MMD. In the ischemic type of the disease, lacunar infarcts can be seen as the areas of hypodensities. When contrastenhanced, tortuous and curvilinear vessels in basal ganglia can be visualized which represent the moyamoya vessels.

Magnetic Resonance Imaging and Angiography [MRI and MRA].

MRI and MRA provide visualization of the arterial tree without being invasive as conventional angiography. In addition to this, MRI also helps demonstrate small


**Table 2.**

*The classification and scoring based on the MRA findings- Score of each artery.*


## **Table 3.**

*The classification and scoring based on the MRA findings – MRA total Score.*

subcortical lesions that are difficult to identify on the CT scan. MRA helps to identify the stenotic distal end of the internal carotid artery, small moyamoya vessels and dural anastomosis between external carotid arteries and vessels of the posterior circulation.

The classification and scoring based on the MRA findings are given above in **Tables 2** and **3**. This MRA scoring system also finds its place in the 2012 Guidelines for the Diagnosis and Treatment of MMD in Japan [5].

## **7.3 Ultrasonography**

In patients with moyamoya disease, the involvement of many extracranial arteries like external carotid arteries, aorta, pulmonary artery, celiac artery, and renal artery has been described. Characteristic signs like ' champagne bottleneck sign' seen due to reduction in the diameter of proximal ICA and 'diamond reversal sign' due to smaller ICA diameter compared to external carotid artery have been demonstrated [31].

Though all the diagnostic modalities contribute to identifying and staging abnormal vasculature, angiography remains the mainstay of diagnosis. It is also helpful in documenting the postoperative resolution of moyamoya.

Electroencephalography [EEG].

The following EEG findings have been seen in moyamoya disease [32]:

