Prolonged disorders of consciousness (DOC) are considered to be among the most severe outcomes after acquired brain injury. Medical care for these patients is mainly focused on minimizing complications, given that treatment options for patients with unresponsive wakefulness or minimal consciousness remain scarce. The complication rate in patients with DOC is high, both in the acute hospital setting, as in the rehabilitation or long-term care phase. Hydrocephalus is one of these well-known complications and usually develops quickly after acute changes in cerebrospinal fluid (CSF) circulation after different types of brain damage. However, hydrocephalus may also develop with a significant delay, weeks, or even months after the initial injury, reducing the potential for natural recovery of consciousness. In this phase, hydrocephalus is likely to be missed in DOC patients, given that their limited behavioral responsiveness camouflages the classic signs of increased intracranial pressure or secondary normal-pressure hydrocephalus. Moreover, the development of late-onset hydrocephalus may exceed the period of regular outpatient follow-up. Several controversies remain about the diagnosis of clinical hydrocephalus in patients with ventricular enlargement after severe brain injury. In this article, we discuss both the difficulties in diagnosis and dilemmas in the treatment of CSF disorders in patients with prolonged DOC and review evidence from the literature to advance an active surveillance protocol for the detection of this late, but treatable, complication. Moreover, we advocate a low threshold for CSF diversion when hydrocephalus is suspected, even months or years after brain injury.