**2.3. Location**

OA preferentially developed in the cerebral hemispheres with a frequency that correspond‐ ed to the relative size of the cerebral lobes (frontal, temporal, parietal, and occipital) [1]. It commonly arose in the supratentorial regions. Occasional locations were insula, diencepha‐ lon, and spinal cord whereas cerebellar location was very uncommon.

#### **2.4. Clinical features**

The most common symptoms were seizure, headache, and personality changes.

#### **2.5. Neuroradiological features**

On magnetic resonance imaging (MRI), OA was described as characterized by a mass which is typically hypointense on T1-weighted images and hyperintense on T2-weighted images. No enhancement is observed on Gadolinium enhanced T1-weighted images (**Figure 1A**, **B**).

**Figure 1.** Magnetic resonance imaging (MRI) of 20-years old woman. A – OA, T1-weighted sequence after gadolinium contrast enhancement (arrow); B – Id, hyperintensity in T2-weighted sequence.
