Normal Pressure Hydrocephalus
Jill C. Cash
A.Idiopathic normal pressure hydrocephalus (NPH) is characterized as a communicating hydrocephalus with ventricular enlargement and a normal opening pressure on lumbar puncture (LP). Idiopathic NPH, a slowly progressive clinical complex, results in a triad of symptoms: gait disorder, urinary incontinence, and dementia.
B.Secondary NPH is caused by an obstruction or noncommunication within the ventricles that prevents the circulation of cerebral spinal fluid and results in hydrocephalus.
Incidence
Idiopathic NPH is considered a rare condition when compared with other causes of dementia. Different studies report the incidence from 2 to 20 million per year. Misdiagnosis or delayed diagnosis is common. Idiopathic NPH is more common between the ages of 60 to 70 years. Approximately 50% of NPH have secondary causes. Both genders are affected equally.
Pathogenesis
Cerebrospinal fluid (CSF) is produced by the choroid plexus and flows from the third and fourth ventricles into the subarachnoid spaces and into the venous circulation. Impaired absorption of CSF results in ventricular enlargement. Several mechanisms of idiopathic NPH have been suggested including congenital, compensated hydrocephalus present since birth and becoming symptomatic later in life, normal CSF production but decreased CSF absorption, retrograde flow into the internal jugular veins increasing central venous pressure, and vascular risks such as hypertension (HTN) and peripheral vascular disorders. The major causes of secondary NPH are subarachnoid hemorrhage (SAH), head trauma, tumor, and meningitis.
Predisposing Factors
A.Most common:
1.Age—most common between ages 60 and 70.
2.Systemic HTN.
3.Peripheral vascular disease.
4.Arteriosclerotic cardiac disease.
B.Probable:
1.Diabetes mellitus.
Common Complaints
A.The three classical features are:
1.Gait—slow, cautious, shuffling, with small steps and a wide base with increased truncal swaying and unsteadiness, unstable turning, and difficulty initiating steps (magnetic gait). This feature must be present for diagnosis of NPH.
2.Urinary incontinence—urgency may occur at onset progressing into incontinence.
3.Cognitive impairment—slowly progressive; becomes evident following gait dysfunction. Includes psychomotor slowing, apathy, forgetfulness, decreased attention and bradyphrenia (slowness of thought).
B.Symptoms and symptoms that are prominently absent include the following:
1.Elevated opening pressure on LP.
2.Complaints of headache.
3.Nausea or vomiting.
4.Papilledema.
C.Comorbidities commonly present in older persons that impact on clinical presentation and outcomes:
1.Musculoskeletal conditions such as osteoarthritis of the knees, hips, or spine.
2.Urinary disorders—previous urinary tract problems including frequency, nocturia, infection, and large post void residual.
3.Cerebrovascular disorders including Binswanger disease, a form of vascular dementia.
5.Vascular disorders including hyperlipidemia, diabetes, obesity, and physical inactivity.
4.Alzheimer’s disease (AD).
5.Parkinson’s disease (PD).
Subjective Data
Family members or significant others are a good resource for obtaining an accurate history:
A.Determine the onset and presentation of gait disorder.
B.Note characterization of gait and its similarity and difference from Parkinson’s disorder.
C.Note onset, course, and characterization of urinary incontinence.
D.Review past medical history of comorbid disorders and treatment protocols, recent acute physical illness, head trauma, hemorrhage, or meningitis.
E.Note evidence of difficulty with attention and concentration (digit span and arithmetic progression). General orientation and general memory spared when compared with Alzheimer’s dementia.
F.Note evidence of forgetfulness, decreased attention span, inertia, and bradyphrenia.
G.Note if patient is able to carry on activities of daily living (ADLs) and instrumental activities of daily living (IADLs), such as using the telephone, shopping, preparing meals, taking medications and handling finances.
H.Review the patient’s medication history and compliance, especially those with anticholinergic side effects, herbal remedies, and over-the-counter (OTC) medications.
I.Assess the patient for nutritional status and dietary intake.
J.Assess depressive symptoms such as insomnia, anhedonia, and sense of worthlessness and hopelessness.
Physical Examination
A.Check: blood pressure (BP), pulse, respirations, height, and weight.
B.Inspect: Overall status for hygiene, nutritional status, and mood.
C.Palpate: Chest, abdomen, and joints.
D.Auscultate: Lungs, heart, and abdomen.
E.Neurologic exam: Perform complete neuro exam. Note facial asymmetry, gait, and balance:
1.Check deep tendon reflexes (DTRs); assess for hyperreflexia.
2.Assess cranial nerves (CNs), II–XII.
3.Assess muscle strength/tone, testing upper and lower extremities for increased tone (spasticity), tremors, and/or decreased tone.
4.Assess sensory response, testing perception for sharp versus dull stimulus, heat versus cold stimulus, local pain perception, proprioception, and evaluate sense of vibration with tuning fork.
5.Note gait, posture, coordination, and balance.
F.Perform Standardized Mini-Mental State Examination (SMMSE) screening test:
1.Mini-Mental State Examination (MMSE). Available at www.uml.edu/docs/Mini%20Mental%20State%20Exam_tcm18-169319.pdf.
2.Montreal Cognitive Assessment (MOCA). Available at www.Mocatest.org.
3.Saint Louis University Mental Status (SLUMS) Examination. Available at medschool.slu.edu/agingsuccessfully/pdfsurveys/slumsexam_05.pdf.
4.Mini-Cog. Available at www.mini-cog.com/mini-cog-intrument/standardized-mini-cog-instrument.
5.Hachinski Ischemia Score. Available at www.strokecenter.org/wp-content/uploads/2011/08/hachinski.pdf.
6.Rule out other specific causes of dementia, including cerebrovascular disease.
G.Complete depression screening:
1.Geriatric Depression Scale (GDS). Available at https://consultgeri.org/try-this/general-assessment/issue-4
2.Beck Depression Inventory. Available at www.enhertsccg.nhs.uk/sites/default/files/pathways/Beck%27s%20Depression%20Inventory_0.docx.
3.Katz Index of Independence in ADLs. Available at https://www.alz.org/careplanning/downloads/katz-adl.pdf.
4.The Lawton Instrumental Activities of Daily Living (IADL). Available at https://consultgeri.org/try-this/general-assessment/issue-23.pdf.
Diagnostic Tests
A.Diagnostic cerebral spinal fluid removal—either large volume LP and/or external lumbar drainage.
B.Complete blood count (CBC) with differentials.
C.Chemistry profile.
D.Thyroid function tests.
E.B12 and folate levels.
F.Vitamin D levels.
G.Venereal disease research laboratory (VDRL) syphilis.
H.Ceruloplasmin—copper test.
I.AB42, tau, phospho-tau.
J.MRI preferred; or CT.
K.Cisternography—nuclear medicine test demonstrates impaired draining of CSF from lateral ventricles in 48-hour period. Ventriculomegaly—hallmark finding on either MRI or CT scan is the absence of, out of proportion enlargement of the sulci and with no evidence of obstruction at the level of the third or fourth ventricles. While not considered specific to NPH, the degree of cortical atrophy helps to distinguish NPH from age-related ventricular enlargement.d.
Differential Diagnoses
A.NPH.
B.AD.
C.PD.
D.Parkinson’s plus disorders (progressive supranuclear palsy; multiple system atrophy).
E.Chronic alcoholism.
F.Multiinfarct dementia.
G.Subdural hematoma.
H.Tumor.
I.Hypothyroidism.
Plan
A.Levodopa challenge may be given to rule out idiopathic PD (no significant response with NPH).
B.Preparations for shunt procedure or LP drainage as determined by neurologist and/or neurosurgeon
C.Discuss therapy options, its benefits, risk factors, and possible outcomes.
D.Provide supportive measures as required based on the patient’s ability to provide self-care based on results of ADL and IADL evaluation.
E.Ensure that the patient is in a safe environment and has appropriate assistive devices for ambulation and protective padding on knees and/or hips to reduce injury with fall incidences.
F.Encourage daily exercise. Physical therapy may be beneficial.
G.If shunt procedure done, appropriate follow-up care of shunt and monitoring for shunt complications including overdrainage, infection, and shunt failure.
Patient Teaching
A.The benefits and risks associated with the shunt procedure.
B.Review signs and symptoms that alert the patient and significant others of shunt complications.
C.Stress that improvement of symptoms do not always occur with shunting.
D.Point out that improvements occur over several months and benefits of shunt may last for several years.
E.More improvement occurs with gait than with cognition.
F.Encourage support groups for the patient and significant others.
Medications
A.No specific medications are helpful for NPH.
B.Medications that are prescribed for established comorbid disorders.
C.Medications usually prescribed for patients with established Alzheimer’s disorder may be prescribed.
D.Medication for depression if screening tests for depression are positive. Escitalopram (Lexapro), sertraline (Zoloft), or paroxetine (Paxil) may be prescribed. Monitor selective serotonin reuptake inhibitor (SSRI) for weight loss and do not use with monoamine oxidase (MAO)-I.
Follow-Up
A.Follow-up on improvement of gait, urinary incontinence, and cognition.
B.Monitor shunt function and changes that may indicate that shunt is not functioning properly.
C.Follow-up mental status tests to determine cognitive improvements.
Consultation/Referral
A.Consider referral to a home health nurse, physical therapy, and social work to develop a working plan for home care to optimize function and reduce caregiver stress.
B.Consider a referral to an access living expert that can evaluate and make recommendations about changes/improvements in the residence to prevent injuries and maintain a degree of independence.
Individual Considerations
A.Geriatrics:
1.NPH is a condition of older persons, primarily ages 60 to 70.
2.Persons afflicted with NPH will have normal agerelated changes as well as other comorbidities, especially arteriosclerotic vascular disorders, that make a diagnosis of NPH difficult to isolate, diagnose, and treat.
B.Even if idiopathic NPH is the established diagnosis without other comorbidities, treatment and full resolution of symptoms, especially cognition, are not possible:
1.Current research indicated evidence that ventriculoperitoneal (VP) shunting is effective, safe, and recommended for geriatric patients diagnosed with NPH. One to three months post-VP surgery the following beneficial outcomes were reported:
a.CSF protein concentration associated with antioxidation and antiaging increased, which suggested the brain might be less predisposed to neurodegeneration.
b.CSF proteins associated with inflammation and toxins decreased.
c.Gait analysis revealed lower cadence, longer step length, and increased single-limb support.
d.Overall balance improvement and stable ambulation.
2.Brain comorbidities such as AD will affect outcomes of NPH treatment. The gait may not improve, stride time variability could continue to deteriorate, and apathy might not show signs of improvement. However, consider the benefits of decreasing/resolution of other symptoms such as headache, blurry vision, bladder control, nausea, lethargy, irritability and imbalance, which all would improve quality of life (QOL).
3.The Hydrocephalus Association has a support website and mobile app for NPH patients and caregivers. It is found at www.hydroassoc.org.