The authors present the case of a 3-year-old girl with a history of myelomeningocele repair, ventriculoperitoneal (VP) shunt placement for hydrocephalus, and shaken baby syndrome who presented in a hypernatremic state as a result of dehydration. At the time of presentation, the patient had experienced a 1-week-long history of diarrhea associated with antibiotic agents used to treat a coexisting pyelonephritis. On admission, the patient exhibited signs and symptoms of dehydration and was discovered to have profound hypernatremia with a serum sodium level of 180 mmol/L. A computerized tomography (CT) scan of the head revealed ventricular enlargement compared with previous imaging findings. A shunt tap revealed intracranial hypotension with good proximal flow. The child was treated for her hypernatremic state, and her neurological condition returned to baseline level. Subsequent CT scans of the head demonstrated a return of the ventricular system to its premorbid size. On the basis of the initial radiographic presentation and subsequent evaluation, the authors hypothesize that the ventricular enlargement was a result of hypernatremia. The signs and symptoms were similar to those found in patients with a VP shunt obstruction; however, a shunt tap revealed intracranial hypotension and excellent proximal flow. To the authors' knowledge, there has not been a radiographically documented case of reversible ventricular enlargement associated with hypernatremia.