113 Normal Pressure Hydrocephalus

Remi Nader

Fig. 113.1 (A–C) Sequential axial T1-weighted magnetic resonance images of the brain with infusion of intravenous contrast. (D) A T2-weighted axial image at the level of the lateral ventricles is shown.

Clinical Presentation

A 64-year-old woman with dementia and a history of previous head injury ~30 years ago presents with progressive deterioration in her mental status with further dementia as well as incontinence over the past year.

Over the past 2 months, she has been having some in creased drowsiness as well as decreased appetite and some weight loss. She is becoming more agitated.

She has had some decreased vocalization in the past year.

The patient has been nonambulatory for ~6 months.

The remainder of her neurologic examination is within normal limits.

Magnetic resonance imaging (MRI) is obtained and pertinent images are shown in Fig. 113.1.

Questions

Interpret the MRI.
Provide a differential diagnosis and the most likely diagnosis.
What are the main clinical criteria for the most likely diagnosis?
What is Evans’ ratio?
What other conditions predispose to this diagnosis?
What diagnostic studies can confirm this diagnosis?
What are the limitations of these studies?
What treatment measures are available for this condition?
What are the main complications of these treatment measures?
Name some prognostic factors for the treatment of this condition.

Answers

Interpret the MRI.

MRI shows diffuse brain atrophy and ventriculomegaly.
The degree of ventriculomegaly appears to be disproportionately elevated compared with the amount of atrophy.
There appears to be some transependymal cerebrospinal fluid (CSF) transudation in the form of periventricular high signal on T2-weighted images.

Provide a differential diagnosis and the most likely diagnosis.

Normal pressure hydrocephalus (NPH) – most likely

Differential diagnosis of dementia includes (mnemonic is “CITTEN DIVA,” more common conditions are in boldface)1,2

Congenital/developmental: Huntington disease

Infectious: syphilis, human immunodeficiency virus (HIV), meningitis, herpes encephalitis

Traumatic: posttraumatic dementia, concussion, chronic subdural hematoma, hypoxia

Tumor: metastatic disease, carcinomatosis

Endocrine: Addison disease, Cushing syndrome, diabetes mellitus, thyroid and parathyroid disease, renal failure

Neurologic: Alzheimer disease, Parkinson, Pick dementia

Drugs/medications: alcohol induced, vitamin B12 or folate deficiency, pellagra, vitamin B1 deficiency

Inflammatory: multiple sclerosis, prion disease

Vascular: diffuse small vessel disease, stroke

Acquired and other: depression, psychosis
What are the main clinical criteria for the most likely diagnosis?
- The Adams triad includes³
  - Ataxia: precedes other symptoms, wide based, “glued to the floor,” difficult initiation of gait
  - Dementia: memory, bradyphrenia, bradykinesia
  - Urine incontinence
- Other criteria include male sex, age greater than 60 years, communicating hydrocephalus, normal pressure on lumbar puncture
What is Evans’ ratio?
- The ratio of the maximum width of the frontal horns to the maximum width of the inner table of the cranial vault⁴
- If the ratio is greater than 0.3, then there is a greater likelihood of hydrocephalus.²
What other conditions predispose to this diagnosis?
- Postsubarachnoid hemorrhage
- Posttrauma
- Postmeningitis
- After posterior-fossa surgery
- Tumor, carcinomatous meningitis
- Alzheimer disease
- Aqueductal stenosis
What diagnostic studies can confirm this diagnosis?
- Diagnostic studies are outlined below^2,3,5:
  - CSF “tap” test by performing a lumbar puncture (LP) with removal of 40 to 50 cc of CSF followed by assessment of improvement of cognitive abilities
  - Serial LP
  - Continuous intracranial pressure (ICP) monitoring
  - Lumbar drain placement
  - Radionucleotide cisternography
What are the limitations of these studies?
- Limitations of the studies include the following^2,3:
  - CSF “tap” test has a poor sensitivity (26–62%).³
  - LP : An opening pressure (OP) greater than 10 (but less than 18 mm H₂ O) is associated with a higher response rate to shunting.
  - Continuous ICP monitoring: Normal OP, but pressure peaks greater than 270 mm H₂ O or recurrent B waves are predictors of better prognosis with shunting.
  - Radionucleotide cisternography: Persistence of ventricular activity in a late scan (after 48–72 hours) is associated with a 75% chance of improving with shunting (this is also the case if the ratio of ventricular to total intracranial activity (V/T) is greater than 32%).
What treatment measures are available for this condition?
- Third ventriculostomy (only in cases of obstructive hydrocephalus)3,6
What are the main complications of these treatment measures?
- Complication rate of shunting in NPH is 30–40%. These include³
  - Subdural hematoma 8–17%
    - Higher rate if the patient is older or if a low pressure valve is used
    - Two thirds resolve spontaneously; one third needs evacuation and shunt tying.
  - Shunt infection, obstruction, or disconnection (10–31%)
  - Intraparenchymal hemorrhage
  - Seizure (4%)
Name some prognostic factors for the treatment of this condition.
- The most likely symptom to improve is incontinence, then ataxia, and lastly dementia.
- There is a better response rate if the gait impairment is the primary symptom.^4,5
- Long-term response rate is as high as 75%.⁴
- The response is better if the symptoms are present for a shorter time.⁴
- Some patients (e.g., with Alzheimer disease) will improve for a brief period and then worsen again.