Normal pressure hydrocephalus, or Hakim syndrome: review and update

This review makes the case that idiopathic normal pressure hydrocephalus (iNPH) is an outdated term because new information indicates that the syndrome is less idiopathic and that the cerebrospinal fluid (CSF) pressure of normal individuals is affected by several factors such as body mass index, age, and sex. Our review updates the epidemiology of iNPH and provides a clinical approach to the management of these patients. All the clinical features of iNPH are common in older individuals, and each has many causes, so the diagnosis is difficult. The first step in reaching an accurate diagnosis is to address the possible contributory factors to the gait abnormality and determine what if any role iNPH may be playing. The two best diagnostic tests are neuroimaging and cerebrospinal fluid (CSF) diversion (large volume lumbar puncture or external lumbar drainage) with pre/post gait evaluation. This review provides an update on the growing evidence that vascular disease, impaired CSF absorption, congenital, and genetic factors all contribute to the pathogenesis of iNPH. We suggest replacing the term iNPH with the term Hakim syndrome (HS) in acknowledgement of the first person to describe this syndrome. Lastly, we discuss the improvements in shunt technology and surgical techniques that have decreased the risks and long-term complications of shunt surgery.