Top 5 Symptoms and causes ofhydrocephalusLearn more about Spina Bifidaand Hydrocephalus athttp://www.spinabifida.net
Definition Hydrocephalus means abnormal orexcessive accumulation of CSF inthe intracranial cavity. To understand Hydrocephalus , wehave to take an idea about thecerebrospinal fluid (CSF) circulation.
CSF Circulation CSF is a dynamic fluid, its main functionis to keep the internal environment ofCentral Nervous System (C.N.S)constant. It also play a role in mechanicalprotection of the brain and spinal cord. Because CSF is dynamic fluid it issecreted and reabsorbed continuously.CSF is secreted by choroid plexus, themain bulk of choroid plexus is present inthe Lateral Ventricles, but there ischoroid plexus also in the Third Ventricleand Fourth Ventricle.
CSF Circulation (Cont.) The rate of formation of CSF is about 0.3-0.35 ml/min i.e. it is about 500 cc/dayalthough the constant amount of CSFpresent in the ventricles and subarachnoidspace is about 150 cc. This means thatmost of the amount secreted is reabsorbedagain. CSF pass from lateral ventricles throughForamina of Monro to the third ventricle,then through Aqueduct of Sylvius to thefourth ventricle ( Fig. 1).
CSF Circulation (Cont.) The fourth ventricle have three aperturesor foramina, One mid-line (Foramen ofMagendi) and two lateral foramina(Foramena of Luschka) (Fig. 2). Throughthese Foramina CSF passes from theventricular system to the subarachnoidspace . It accumulate first in Cisterna Magna, partof CSF descends downwards around thespinal cord, but the majority passesupwards through the Tentorial Hiatus overthe surface of both cerebral hemispheresto be absorbed by the Arachnoid villi in theSuperior sagittal sinus (SSS).
CSF Circulation (Cont.) So, CSF is secreted from the bloodby choroid plexus and reabsorbed inthe blood by Arachnoid villi, thisexplains the physiological dynamicfunction of CSF that keeps theinternal environment of CNSconstant. ( Fig. 3).
Pathogenesis ofHydrocephalus Any disturbance in CSF secretion,circulation and absorption will results inabnormal accumulation, so thepathogenesis may be : Obstruction of CSF pathway (mainfactor). Excessive formation of CSF as in case ofchoroid plexus papilloma ( rare ). Decreased absorption as in SSSthrombosis around arachnoid villi.
Etiology of CSF pathwayObstruction Congenital anomalies: this is Commonlyseen in the area of Aqueduct, such asforking of Aqueduct, gliosis or obstruction.N.B. CNS is the commonest system in thebody liable to congenital anomalies. Post–traumatic or Post–Hemorrhagic:Subarachnoid hemorrhage, whetherspontaneously (as in Ruptured Intracranialaneurysm or AVM) or after head traumamay result in inflammatory reactions,adhesions, and obstruction ofsubarachnoid space and so Hydrocephalus
Etiology of CSF pathwayObstruction (Cont.) Post–Inflammatory or Post-meningitic:Inflammation of Meninges usually heals byFibrosis and adhesions within thesubarachnoid Spaces, so obstruction ofCSF pathway. Neoplasm: Any abnormal mass such astumor or abscess along the pathway ofCSF may result in obstruction.N.B: In some cases of Hydrocephalus, wecan not diagnose the underlying etiologicalcause, this is what is called Hydrocephalusof undetected cause. These cases aremostly due to mild unnoticed Head traumaor sub clinical Meningitis.
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