Normal Pressure Hydrocephalus

1. See Also
   1. Hydrocephalus
2. Pathophysiology
   1. See Cerebrospinal Fluid
   2. Defined as communicating Hydrocephalus
      1. No obstructive mass
   3. Results from decreased CSF absorption
      1. Due to scarring or fibrosis of arachnoid granulations
   4. Pressure builds within ventricles
      1. Baseline pressure higher but in normal range
   5. CSF production decreases
   6. Ventricles distend
      1. Stretch nerve fibers
      2. Compress periventricular tissue including vessels
   7. Brain parenchymal ischemia
3. Causes
   1. Idiopathic fibrosis in most cases
   2. Contributing causes in some cases
      1. Subarachnoid Hemorrhage
      2. Head Injury
      3. Meningitis
4. Symptoms and signs
   1. Classic triad (Positive Predictive Value: 65%)
      1. Gait instability
      2. Urinary Incontinence
      3. Dementia
   2. Gait instability (gait Apraxia)
      1. Most common initial symptom
      2. Short shuffling steps (feet glued to floor)
      3. Wide based, slow ambulation
   3. Urinary Incontinence
      1. Urinary urgency
      2. Urodynamics: Detrussor muscle ineffective contraction
   4. Subcortical Dementia
      1. Late finding, and least responsive to shunting
      2. Findings
         1. Inattention
         2. Recall latency (but memory is accurate)
         3. Loss of spontaneity
      3. Cortical findings are not seen in NPH Dementia
         1. No difficulty with word formation (Aphasia)
         2. Able to interpret stimuli (Agnosia)
         3. No difficulty with sequential tasks (Apraxia)
5. Differential Diagnosis
   1. See Hydrocephalus
   2. See Overflow Incontinence
   3. See Dementia
   4. See Parkinson's Disease
6. Radiology
   1. MRI Head
      1. Ventriculomegaly
      2. Cerebral parenchyma preserved
         1. Contrast with Alzheimer's Disease
      3. Medial hippocampus and Temporal Lobe preserved
         1. Contrast with Alzheimer's Disease
   2. Cine MRI (CSF flow imaging)
      1. Turbulent posterior Third Ventricle flow
      2. Turbulent aqueduct of Sylvius flow
   3. Radionuclide cisternography
      1. Used to evaluate for communicating Hydrocephalus
7. Diagnostics
   1. Routine Lumbar Puncture
      1. Evaluates differential diagnosis
      2. Normal CSF Exam
         1. Normal CSF Protein
         2. Normal CSF Glucose
         3. CSF Opening Pressure <200 mm H2O
   2. High volume Lumbar Puncture
      1. Assess symptoms before/after removing 30-60 ml CSF
      2. Predictive of response to shunting
   3. Prolonged lumbar drainage
      1. CSF removed over 3-5 days via pump
      2. Predictive of response to shunting
   4. Intracranial Pressure monitoring
      1. May identify intermittent spikes in CSF Pressure
   5. CSF outflow
      1. Saline infused 0.5-5 ml/min via Lumbar Puncture
      2. Intracranial Pressure measured via ventriculostomy
      3. Observe for elevated outflow resistance
         1. May predict shunting response
8. Management: Ventriculoperitoneal shunting
   1. Description
      1. Catheter in Lateral Ventricle
      2. Cap and valve placed below scalp
      3. Tubing tunneled SQ from valve to Abdomen
      4. CSF diverted from ventricle to peritoneum
   2. Efficacy
      1. Variable based on patient selection
   3. Predictors of good response to shunting
      1. Patients with known NPH etiology do best
      2. Symptoms present only for short time
      3. No Dementia or mild Dementia present
      4. Diagnostics predictive of good response
         1. High volume Lumbar Puncture
         2. Prolonged lumbar drainage
9. References
   1. Vanneste (2000) J Neurol 247:5-14
   2. Verrees (2004) Am Fam Physician 70:1071-86