Reason: History of arachnoid cyst and fenestration. Evaluate CSF flow thru fenestration. new increasing headaches. History: new worsening headachesAdditional history from EMR: Chronic hydrocephalus due to temporal tip arachnoid cyst herniating against the brainstem causing aqueduct stenosis. Status post endoscopic third ventriculocisternostomy and endoscopic fenestration of temporal tip arachnoid cyst on the right side, 7/2/2007. Images are slightly limited by patient motion. There is a stable right frontal approach ventriculostomy catheter, with its tip along the lateral aspect of the mid right lateral ventricle. Susceptibility from the shunt limits evaluation of surrounding structures. While the fourth ventricle remains normal in size, lateral and third ventriculomegaly is essentially stable. No residual or recurrent arachnoid cyst is identified along the medial right middle cranial fossa, although there remains slight asymmetric prominence of subarachnoid space along the floor of the right middle cranial fossa. Septum pellucidum remains absent.CSF flow does not include the area of the previously seen arachnoid cyst. However, with regards to the third ventriculostomy site, a T2 hypointense flow-void is not visualized on the 3-D T2 weighted images. However, 3-D T2 weighted images do suggest attenuation of the floor of the third ventricle as suggested on 1201/32 although this is to the right of midline. There is questioned very faint biphasic CSF flow suggested slightly more posteriorly to the suspected area of surgery (1302/63-65). Regardless, the appearance is similar to prior exams.Biphasic flow is identified ventral to the brainstem and cervical spinal canal, and to a lesser degree along the dorsal upper cervical spinal canal. Only faint biphasic flow is seen along the cerebellar tonsils. The cerebellar tonsils have a pointed configuration, especially on the left where they extend 6 mm below the level of the foramen magnum. The foramen magnum does not appear crowded. Dysmorphic cerebral parenchyma appears similar, with areas of thinning noted, especially involving the periventricular white matter along the left occipital pole. Previously noted susceptibility in the left occipital horn has resolved, although there is persistent susceptibility along the right medial thalamus, decreased in extent. The basal cisterns remain patent. There is no diffusion abnormality. No extra-axial fluid collection is identified.Normal flow-voids are demonstrated in the major intracranial vascular structures. There is diffuse thinning of the corpus callosum, relating to chronic hydrocephalus. The remainder of the midline structures and craniocervical junction are within normal limits. There is a right lateral sphenoid mucosal retention cyst.
1. Stable appearance of lateral and third ventriculomegaly consistent with chronic obstructive hydrocephalus. No definite evidence of recurrent right middle cranial fossa arachnoid cyst although there remains slight asymmetric prominence of the subarachnoid space inferior to the right temporal lobe. Please note that CSF flow is not obtained through the area of cyst fenestration.2. CSF flow not well visualized through the expected location of third ventriculostomy, although there may be faint biphasic flow identified just posteriorly, similar to prior exams.3. CSF flow visualized along the ventral brainstem and upper cervical cord as well as at the level of the foramen magnum dorsally, although the dorsal flow appears slightly less well visualized compared to prior exam. Redemonstration of pointed cerebellar tonsils although ample CSF space is seen at the foramen magnum level. Please correlate clinically.