Hydrocephalus, defined as the accumulation of cerebrospinal fluid (CSF) in the brain, may occur in the setting of obstructed CSF flow throughout the ventricular system, in which case the term obstructive hydrocephalus is used. Signs and symptoms depend on the age of the patient and the underlying cause. A comprehensive clinical and imaging workup is necessary to make the diagnosis and determine the causes of CSF obstruction.
Obstructive hydrocephalus is broadly defined as an abnormal accumulation of CSF in the brain due to obstruction of CSF flow   . The obstruction can occur at virtually any point of the CSF pathway, including the ventricular system (the lateral, 3rd and 4th ventricle, as well as the foramen of Monroe and the Sylvian aqueduct) and the subarachnoid space, and numerous etiologies have been established . Intracranial hemorrhage (particularly in neonates and infants), infections (bacterial meningitis, but also intrauterine infections by toxoplasma gondii, cytomegalovirus and enteroviruses), and tumors are some of the more common causes, while progressive enlargement of the 4th ventricle (known as Dandy-Walker malformation), Arnold-Chiari malformation of the cerebellum, and a range of genetic disorders are also described as causative agents of obstructive hydrocephalus    . In infants and neonates, a disproportionate head growth, bulging fontanelles, markedly wider separation of the cranial sutures, and paresis of upward gaze (the "setting sun" of the eyes) are typical signs of hydrocephalus that may be accompanied by poor feeding, irritability, and a delayed maturation   . On the other hand, headaches, vomiting, visual deficits, and drowsiness are encountered in adults and older children in the setting of hydrocephalus, whereas hypertension, bradycardia and respiratory difficulties signify severe obstruction of CSF flow  . In addition to the acute symptomatology, hydrocephalus might also cause chronic symptoms, such as behavioral and cognitive changes, delayed puberty, and defects of higher brain functions  . In either case, a prompt diagnosis could significantly reduce the risk for the patient, and might even be life-saving.
Because hydrocephalus may lead to both short-term and long-term disability, early recognition is vital. Physicians should obtain a detailed patient history that will reveal when did the symptoms start and how did they progress, which is particularly important in neonates and younger children. If the physical examination reveals prominent cranial changes and detect respiratory, but also cardiac abnormalities, a valid clinical suspicion toward hydrocephalus as the underlying cause of symptoms can be made. Imaging studies, however, are the cornerstone in confirming hydrocephalus and the exact type, but also in identifying the condition that induced it. Because of its accessibility, non-invasiveness, and reliability in the youngest population with an open fontanelle, ultrasonography should be readily used in neonates, as it provides a direct view of the ventricular system and reveals the presence of a mass (eg. hematoma) that obstructs normal CSF flow  . Otherwise, computed tomography (CT) and magnetic resonance imaging (MRI) are recommended during the diagnostic workup    . Some of the most common features encountered in these studies are ventricular dilation and edema of the periventricular white matter (as a result of spinal fluid resorption), but their ability to confirm the exact location of the obstructive lesion is vital for both diagnostic and therapeutic purposes   . Additionally, diffuse-weighted (DW) MRI imaging has proven to be of even greater benefit when patients are suspected to suffer from hydrocephalus, and this technique should be employed whenever possible .