Normal pressure hydrocephalus or progressive supranuclear palsy? A clinicopathological case series
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Idiopathic normal pressure hydrocephalus (iNPH) is a poorly understood condition, which typically presents with the triad of balance impairment, urinary incontinence and subacute cognitive decline, while brain imaging shows a marked enlargement of the cerebral ventricles. Few patients with iNPH have come to post-mortem. We identified four patients from the Queen Square Brain Bank archival collection, who had received a diagnosis of iNPH during life, and reviewed their clinical, radiological and pathological characteristics. At post mortem examination, one patient had Parkinson’s disease (PD) while the other three had progressive supranuclear palsy (PSP). All four had presented with pure akinesia with gait freezing, accompanied by unsteadiness and falls. An awareness that PSP or PD can mimic the clinical symptoms of iNPH may help to avoid invasive and futile cerebrospinal fluid shunting procedures.
KeywordsNormal pressure hydrocephalus (NPH) Progressive supranuclear palsy (PSP) Ventriculo-peritoneal (VP) shunt Pure akinesia with gait freezing (PAGF) Alzheimer’s disease (AD)
Normal pressure hydrocephalus (NPH) is a clinical syndrome characterised by unsteadiness of gait, urinary incontinence and cognitive decline, which can respond to cerebrospinal fluid (CSF) drainage . The radiological “hallmark” of NPH is markedly enlarged ventricles in the absence of involutional change in the brain. NPH has been categorized as either idiopathic (iNPH) or secondary (following head trauma, intracranial haemorrhage, tumour, meningitis or complication of cranial surgery).
iNPH remains a controversial entity, and of the relatively few patients coming to autopsy, a significant proportion have been noted to have co-existing neurodegenerative or vascular pathologies [2, 3]. Whether those pathologies are the primary cause of the syndrome or an additional incidental disease process in the elderly population affected is uncertain.
Two recent reviews have reported the post-mortem findings of 38 patients that had been clinically diagnosed with iNPH with vascular changes (71 %), Alzheimer’s disease (AD) (61 %), progressive supranuclear palsy (PSP) (2.6 %) and corticobasal degeneration (CBD) (2.6 %) being the most frequent co-existing pathologies. None of these patients had iNPH as the only final clinical diagnosis [2, 3] and no specific neuropathological changes for iNPH were identified . Some of the patients had an unsuccessful shunt procedure, raising questions about the accuracy of diagnosis in these particular cases.
In a prospective study of 37 patients who underwent shunting for iNPH, a high prevalence of AD pathology was found in cortical biopsies obtained during shunt insertion. Patients with moderate to severe pathology failed to demonstrate benefit on any study measures assessing gait, cognition and bladder control at 4 months follow-up .
Hydrocephalus in elderly rats can induce both amyloid beta (Aβ) and phosphorylated tau accumulation in a pattern similar to human AD. CSF dynamics also appeared to impair Aβ clearance as a result of impaired CSF circulation .
In the present study, we aimed to review the clinical, radiological and pathological characteristics of four patients who had received a clinical diagnosis of iNPH.
We reviewed the database of 1,450 brains in the Queen Square Brain Bank (QSBB). The retention of and access to clinical records and pathological material at QSBB has generic ethical approval from the London Multi-Centre Research Ethics Committee.
Our inclusion criteria were patients aged 50 years or above exhibiting: (1) presence of at least two of the following symptoms or signs (a) a progressive gait impairment, (b) severe urinary difficulties, (c) cognitive decline; and (2) markedly enlarged cerebral ventricles on computer tomography (CT) or magnetic resonance imaging (MRI) of the head who underwent an invasive diagnostic (high volume lumbar puncture) or therapeutic procedure (insertion of a ventriculo-peritoneal [VP] shunt)  for the evaluation or treatment of suspected NPH. Patients with a history of congenital hydrocephalus, venous sinus thrombosis, central nervous system infections or obstructive lesions were excluded.
A systematic review of all available medical records was performed. Case notes were reviewed by one of the authors (NKM). The neuropathological diagnosis of all cases was made by a neuropathologist at the QSBB (JH or TR). Case 3 has been previously published .
Table showing clinical characteristics of four patients initially diagnosed with normal pressure hydrocephalus
Case 3 
Age of onset (years)
Difficulty walking, unsteadiness
Poor mobility, recurrent falls
Disease duration at presentation
Initial clinical features
Generalised slowing down, no tremor, postural instability, deterioration in handwriting, but no micrographia
Mild cognitive impairment, dysarthria, generalised slowing down, no tremor, brisk lower limb reflexes
Hypomimia, no hypophonia, slow and broad-based gait, difficulty in gait initiation and turning, mild right sided rigidity and bradykinesia, no tremor, micrographia
Unsteady gait, tendency to veer to the left, no tremor or rigidity, mild urinary urgency and occasional incontinence, mild cognitive decline and bradyphrenia, micrographia
Late clinical features
Severe hypomimia and hypophonia, severe axial and mild symmetrical limb rigidity, no bradykinesia, freezing, positive Applause sign, significant cognitive decline (MMSE 14/30)
Slurring dysarthria and hypophonia, mild symmetrical limb rigidity and bradykinesia, wide-based unsteady gait, bradyphrenia and cognitive decline, grasp and palmomental reflexes bilaterally
Mild hypomimia, moderate hypophonia and dysarthria, gait initiation failure and freezing, severe axial and moderate symmetrical limb rigidity, mild bradykinesia, bradyphrenia and cognitive decline (MMSE 22/30)
Slurring dysarthria and dysphagia, frontalis overactivity, severe axial rigidity, moderate bilateral cogwheel rigidity, unsteady gait even when using frame, freezing episodes, utilisation behaviour and perseveration, dysexecutive syndrome
Eye movement signs (years after presentation)
Slow hypometric vertical saccades
Marked restriction in vertical eye movements
Slow horizontal and vertical saccades
Reduced vertical gaze
Slow horizontal saccades
Urinary symptoms (years after presentation)
Urinary urgency and incontinence
Urinary incontinence at night
Urinary urgency and incontinence
No record of response
Maximum l-dopa treatment
Response to CSF removal
N/A—VP shunt without a trial of CSF removal
Suggested by neurosurgeons, but advised against by neurologist
Suggested by neurosurgeons, but advised against by neurologist
VP shunt inserted with some improvement in gait and cognitive function
VP shunt inserted with moderate improvement in gait and cognitive function
Secondary NPH risk factors
Anterior cervical decompression for spondylosis, syringomyelia
Initial clinical diagnosis
NPH and secondary parkinsonism
Final clinical diagnosis
Time from initial to revision of diagnosis
Disease duration (y)
Amyloid angiopathy (moderate)
All four patients presented with difficulty walking and falls, postural instability, and mild subcortical or executive dysfunction. Three patients had mild difficulties with swallowing. Case 4 had urinary urgency. Two had risk factors for secondary NPH (Table 1).
Neurological findings of all patients prior to the diagnosis of NPH revealed a slow, broad based and unsteady gait with minimal limb rigidity. None of the patients had tremor or an eye movement abnormality. The Mini-Mental Score Examination (MMSE) ranged from 26 to 28 out of 30.
On neuroimaging (two patients had CTs and two had MRIs), all patients had ventricular dilatation disproportionate to the degree of cortical atrophy on visual assessment. In the second MRI of case 4 (6 years into the disease) midbrain atrophy and the ‘hummingbird’ sign was also noted.
Three patients had transient improvement in 10-m walk and mental tasks (cases 1, 2 and 3) after 13–40 mls of CSF withdrawal. CSF opening pressure was 13 cmH2O in case 1 and 21 cmH2O in case 3. It was not recorded in case 2 as lumbar puncture was done with patient seated. case 4 did not undergo trial of CSF withdrawal prior to VP shunting as gait dysfunction, cognitive decline, urinary disturbance and imaging studies were thought to be highly typical of NPH.
Two patients underwent VP shunting with transient improvement in gait and cognition. In the other two patients (cases 1 and 2), VP shunting was suggested by neurosurgeons but the decision was made by neurologists not to proceed, as they felt there was an underlying co-existing neurodegenerative condition.
All four patients had striking gait instability, falls and freezing initially. Progressive cognitive decline, significant urinary disturbance, eye movement abnormalities, hypomimia and hypophonia occurred later in the disease course. These later features prompted the neurologists that shunt-responsive NPH was not the underlying diagnosis.
We report four patients in whom an initial diagnosis of iNPH was considered and who had at least a transient response to large volume CSF drainage or VP shunt. However, all patients subsequently deteriorated, and further progression of their disease led to the revision of the final clinical diagnosis to PSP. None of the cases had iNPH as their most likely clinical diagnosis at the time of death. One patient had a pathological diagnosis of PD, while PSP was confirmed in the other three cases. The QSBB collection is probably biased towards cases with an unclear clinical diagnosis and this could account for the high prevalence of neurodegenerative pathology among its cases diagnosed as iNPH.
All four patients had presented with gait ignition failure and freezing, a clinical picture most commonly associated with diffuse cerebrovascular disease and less commonly with PSP or PD [8, 9]. The PSP-PAGF (pure akinesia with gait freezing) subtype usually develops vertical supranuclear gaze palsy later in the disease course, and in post-mortem has milder tau pathology when compared to the classical Richardson’s syndrome . In the present series, eye-movement abnormalities also occurred late in the disease course, and thus none of the patients fulfilled the NINDS-SPSP criteria for PSP in the early stages . Furthermore, none of the patients had the “extended lumbar drainage protocol” which is regarded as the gold standard for the presumptive diagnosis of NPH, increasing the chance of long-term benefit from shunting to 80 % .
All of the patients followed a relatively benign disease course, remaining independent until a few months before death, when significant cognitive and mobility impairment, urinary incontinence and, in case 4, severe dysphagia and unintelligible speech ensued.
Excess ventricular expansion with disproportionally large ventricles for the degree of cortical atrophy can occur in PSP . Recurrent falls can also lead to head injuries and subdural haematomas in patients with PSP, resulting in secondary NPH. In our series, two patients carried a risk of developing secondary NPH as a result of previous subarachnoid haemorrhage and syringomyelia warranting spinal surgery. Case 1 had sustained a left neck of femur fracture after a fall.
In a recent Mayo Clinic community-based study, iNPH was found to be relatively rare (1.19 per 100,000 per year) with an incidence approximating that of PSP . Additional or alternative neurologic diagnoses later emerged in 5 of 12 patients, one having pathologically proven PSP. None of these patients had sustained definitive improvement after shunting and in the PSP case, it was speculated that the later-diagnosed disorder had been responsible for the entire clinical picture .
Revised clinical diagnosis for patients diagnosed as iNPH (with VP shunts) in the National Hospital for Neurology and Neurosurgery
Number of patients (n = 24)
PD/atypical parkinsonism/progressive gait apraxia/vascular parkinsonism
AD/vascular dementia/progressive cognitive decline
‘Progression of underlying condition, undergoing investigations’
The transient improvement following CSF removal in all cases raises the question of whether this may be a useful therapeutic strategy in PSP. Although therapeutic CSF drainage has not been used in PSP, it has been used in vascular parkinsonism (VP). Out of 40 patients with VP who were treated with large-volume CSF removal, almost 40 % reported significant gait improvement . Although a placebo response cannot be excluded, one possible explanation for this initial clinical improvement could be renewal of ‘stagnant’ CSF, which increases the ability to ‘clear’ potentially toxic metabolites, such as Aβ or tau proteins. Alteration in ventricular compliance may also cause partly reversible gait dysfunction via disruption of ascending and descending periventricular tracts .
Cognitive impairment in NPH might also be a result of a combination of CSF dynamic disturbance and its resulting biochemical abnormalities . In a recent study of 21 patients with NPH, a combination of Aβ and total tau levels in ventricular CSF predicted favourable surgical outcomes with a sensitivity of 80 % and a specificity of 82.4 % . VP shunting in 35 patients with NPH led to a reduction in CSF neurofilament proteins which are markers of axonal damage, resolution of periventricular white matter hyperintensities (WMH) and clinical improvement in 28 patients 3 months after shunt insertion . In another study, 12 of 17 patients with NPH had parkinsonism (71 %) which significantly improved and, in 11 patients WMH resolved following CSF tap tests or shunt operations . Nevertheless, it is not known if these biochemical, radiological and clinical improvements are sustained in long-term follow-up.
iNPH is uncommon and a diagnosis of exclusion . The absence of urinary incontinence and the presence of a supranuclear gaze palsy in a suspected case of iNPH should lead to reconsideration of the diagnosis and raise the possibility of the PAGF variant of PSP which is unresponsive to shunting.
We wish to thank the donors and their families, without whom this work would not have been possible. We received funding from the Reta Lila Weston Trust.
Conflicts of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
All human studies must state that they have been approved by the appropriate ethics committee and have therefore been performed in accordance with the ethical standards laid down by the 1964 Declaration of Helsinki.