Communicating hydrocephalus with reversible cognitive impairment

To the Editor

A 54-year-old woman with a 13-year history of bipolar affective disorder presented with a 3-year history of urinary incontinence, falls and progressive short-term memory impairment. There was no history of head injury. On mental state examination she presented as mildly disheveled with a ‘magnetic’ wide-based gait. Although she exhibited some psychomotor slowing, her mood was euthymic and there was no evidence of thought disorder or hallucinations. Her speech was prosodic and in conversation she was appropriately concerned about the looming threat of nursing home placement. Following bedside cognitive testing she demonstrated impairments of attention, visual construction, memory and executive function. Language function was unimpaired. Except for her gait, her neurological examination was unremarkable and a differential diagnosis of idiopathic normal pressure hydrocephalus (NPH) was proposed.

On magnetic resonance imaging (MRI), a T2-weighted midline sagittal image (Figure 1A) demonstrated a prominent flow void in the aqueduct of Sylvius (arrow) and outward bowing of the supraoptic and infundibular recesses (star) of the third ventricle. In addition, the corpus callosum was upwardly bowed and the septum pellucidum fenestrated. T2-weighted axial (Figure 1B) and T1-weighted coronal (Figure 1C) images demonstrated characteristic ventriculomegaly with box-shaped frontal horns of the lateral ventricles. The patient proceeded promptly to surgery and a postoperative non-contrast computed tomography (CT) scan demonstrated appropriate placement of a right occipitoparietal shunt (Figure 1D).

Figure 1.

MRI and CT Brain.

Within a week of surgery, the patient demonstrated a significant improvement in continence, mobility and cognition, with normalization of visual construction, memory and executive function. While ventriculoperitoneal shunting does not always improve the clinical syndrome associated with idiopathic NPH, the presence of an increased cerebrospinal fluid (CSF) stroke volume and aqueductal flow void on MRI may predict a favourable outcome (Bradley et al., 1996). Other predictors may include shorter duration of illness (Caruso et al., 1997) and a temporary symptomatic response to the removal of 40 mL CSF by lumbar puncture (Sand et al., 1994).

The appropriate assessment and treatment of this patient averted both a misdiagnosis of young-onset dementia and premature nursing home placement, demonstrating the utility of seeking potentially reversible causes of neuro-cognitive impairment and avoiding the attribution of functional decline to mental illness in an otherwise well-treated individual.