1. E.GAMY-J.MAHLAOUI-T.AMIL-S-CHAOUIR-A.HANINE- M.MAHI-S.AKJOUJ Medical imaging military hospital Mohammed V instruction –Rabat. NR3

2.  Intracranial arachnoid cysts are defined as a pocket full of intra-subarachnoid CSF without communication with the ventricular system.  The aim of this study is to clarify the contribution of computed tomography (CT) and especially MRI.  In the diagnosis with emphasis on information brought by the sequences (diffusion) in the differential diagnosis.

3.  CT scans performed in axial and coronal.  MRI includes the following morphological sequences weighted in T1, T2, FLAIR, and T2 * sequences RELEASE in the different planes.

4.  CT shows a process of expansive cystic lesion that is hypodense and the same signal as cerebrospinal fluid (CSF), which can result in thinning of the cortex next, there is no contrast enhancement.  MRI it has a signal identical to that of (LCS) on the sequences T1 and T2 without contrast. However to make a difference with an epidermoid cyst, FLAIR- weighted sequences, distribution and CISS are a great contribution.

5. CT: CSF density bone remodeling, no contrast enhancement.

6. MRI: T1/T2: iso intense to CSF

7. DWI: no signal no contrast enhancement

8.  There is no causal link between the temporal lobe hypoplasia and arachnoid cysts appear despite their association.  Hypothesis probable abnormalities of embryogenesis that affects  Independently, and the formation of the arachnoid, and the temporal lobe in some patients, is the effect of compression KA.  The search for evidence in favor of either MRI or hypogénésie compression of the temporal lobe by a KA.

9.  In The hypoplasia of the temporal lobe, temporal lobe concave next to the KA,  Discharge of the temporal horn and / or adjacent structures; sinuosity, ripple temporal cortex next to the KA.  Decrease in the volume of adjacent parenchyma.  Not discharge.  No thinning of cortical bone next to the KA.

10.  Epidermoid cyst:  Irregular edge in, is insunie in tanks,  Includes vessels and nerves  Registered in 45% of cases at the basal cisterns.  Light Flair hyperintense signal and Hyper Distribution.  Light Flair hyperintense signal and Hyper Distribution

11.  The chronic subdural hematoma:  Lenticular, higher signal to CSF ​​  Subdural hygroma  CAVITY porencephalic  MEGAGRANDE TANK  MALIGNANT CYSTIC  NEURO-CYSTS ENTERIC  CYST NEUROGLIAL

12.  KA asymptomatic abstention  KA giant symptomatic or asymptomatic high risk of bleeding: - Craniotomy + resection of the outer mb

13.  The MRI allows the diagnosis of intracranial arachnoid cysts with characteristics of specific sequences that can differentiate epidermoid cysts.  With multi planar cuts it offers, it remains the best technique to assess the extent and anatomical relationships of these cysts.