Factors Predicting Response to Shunting in Normal Pressure Hydrocephalus

Factors Predicting Response to Shunting in Normal Pressure Hydrocephalus

The research project is designed to determine which combination of tests will enable physicians to predict whether a patient with symptoms of normal pressure hydrocephalus (NPH) will improve with a shunt.

Normal pressure hydrocephalus (NPH) is a potentially reversible progressive neurological condition disproportionately affecting the elderly population. Given current controversies regarding its exact definition, accurate incidence and prevalence figures are elusive. NPH was first described forty years ago as a triad of symptoms consisting of gait difficulties, urinary incontinence, and memory problems in patients with enlarged ventricles in the absence of increased intracranial pressure (ICP). The cause of primary, or idiopathic NPH (INPH) remains elusive, while secondary NPH results from intracranial insults such as head trauma, meningitis, or intracranial hemorrhage. NPH can be successfully treated with cerebrospinal fluid (CSF) shunting. However, the accurate diagnosis and treatment of patients with NPH remains problematic, despite significant advances in brain imaging and ICP physiology.

Objectives - The primary aims of this study are:

1. to confirm the ability of external lumbar drainage to increase the success rate of selectively shunting patients with NPH compared to historical controls
2. to refine the diagnosis of NPH by determining whether the factors that change before and after lumbar drainage will predict failure to improve after shunting. A related aim is to assess the complications attributable to lumbar drainage.
3. to perform a preliminary evaluation of programmable shunt valves for NPH compared to historical controls using fixed-pressure valves. A related aim is to determine whether post-op objective analysis of gait, cognitive function and urinary symptoms will help refine the programmable shunt setting on an individual basis.

Secondary study aims include:

Investigating the pathophysiology of NPH by: 1) correlating cortical vein compliance measured by MRI flow quantification studies with CSF pressure waveform analysis; 2)assessing funduscopic changes before and during ELD; 3) performing and cross correlating CSF chemical analysis on screening positive and negative patients as well as screening-positive patients who are shunt responsive versus unresponsive.

Inclusion Criteria:

• Walking difficulties in both legs which has developed gradually, not explained by other conditions, either in combination with mental impairment and urinary incontinence
• Brain CT or MRI findings of enlarged ventricles compared to established standards (minimum Evans ratio of 0.30 as measured by reviewing films)
• Mental impairment must be mild to moderate, emerging with or after the walking difficulties
• Age > or = 18 years old
• MMSE (Mini-mental status exam): < or = 10
• Urinary incontinence

Exclusion Criteria:

• No or only minimal walking difficulties combined with severe dementia
• Severe medical problems with limited life expectancy (less than six months)
• Contraindications to surgery
• Lack of informed consent