What Causes Headache , Vomiting And Dizziness?

Dear Doctor my son age 14 had headache, vomited and have giddiness. I bought him to see a doctor. And we did CT scan.
Scan Report Details
CT SCAN OF BRAIN
Serial xial sections of the brain were studied without administraion of I.V. contrast.
5mm slice thickness for demonstration posterior cranial fossa and 10mm slice for the rest of the brain.
Prominent CSF space is seen in the left middle cranial fossa,antero-inferior and medical to the left temporal pole (images 6 to 8). Possibility of arachnoid cyst cannot be ruled out.
*Both orbital contents are normal
*Posterior cranial fossa contents- fourth ventricle.cerebellar hemispheres, vermis brain stem and cerebello-pontine cisterns are normal
*Fissures exhibit normal apperance
*Ventricular system size and configuration is normal
cerebral sulci and gyri re normal
no shift of midline structures is seen
both side mastroid air cells are normal
Nasal septum is minimally bowing to the right side (images 1 to 4)
visualized sinuses appear normal
normal bony calvarium. extra cranial soft tissues are normal
impression
prominent CSF space/ ? archanoid cyst in the left middle cranial fossa, antero inferior and medial to the left temporal pole. thre is no evidence of hydrocephalus or features of cerebral edema. brain stem and cerebellum appear normal correlate clinically.