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---
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title: "Normal-Pressure Hydrocephalus"
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docid: "834ccc3e-2116-4295-8408-0ac9a06bd2ff"
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breadcrumbs:
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- "Nuclear Medicine"
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- "Central Nervous System"
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- "Cerebrospinal Fluid"
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- "Normal-Pressure Hydrocephalus"
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---
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# KEY FACTS
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- ## Terminology
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- Normal-pressure hydrocephalus (NPH): Ventriculomegaly out of proportion to sulcal enlargement in setting of normal cerebrospinal fluid (CSF) pressure
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- ## Imaging
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- In-111 DTPA radionuclide cisternography
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- Used in patients in whom MR is contraindicated and CT is equivocal
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- Protocol
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- Intrathecal injection of In-111 DTPA
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- Obtain planar images with gamma camera immediately after injection and at 4, 24, and 48 hours
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- Normal study
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- 1 hour: Radiotracer reaches basal cisterns
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- 2-6 hours: Radiotracer reaches sylvian fissures
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- 12 hours: Radiotracer reaches cerebral convexities
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- 24 hours: Radiotracer reaches superior sagittal sinus and is absorbed by arachnoid villi
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- Normally no radiotracer enters ventricles, although transient activity in ventricles at 4 hours is still considered normal
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- NPH
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- Radiotracer activity in ventricles at ≥ 24 hours
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- Absence of radiotracer activity in cerebral convexities by 24-72 hours
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- SPECT/CT can help confirm ventricular activity
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- ## Clinical Issues
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- Symptoms: Gait disturbance, urinary incontinence, dementia
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- Treatment: Ventriculoperitoneal shunt
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- ## Diagnostic Checklist
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- Ventricular dilation on anatomic imaging may related to cerebral atrophy or underlying neurodegenerative disease
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- Classic finding of NPH on radionuclide cisternography
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- Prominent ventricular activity at 24-72 hours with absent activity over convexities
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# TERMINOLOGY
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- ## Definitions
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- Normal-pressure hydrocephalus (NPH): Ventriculomegaly out of proportion to sulcal enlargement in setting of normal cerebrospinal fluid (CSF) pressure
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# IMAGING
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- ## Nuclear Medicine Findings
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- In-111 DTPA radionuclide cisternography
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- Advantages
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- Provides physiologic information about CSF flow
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- Useful in patients who cannot receive MR or in whom CT is nondiagnostic (equivocal findings)
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- May help determine who may benefit from ventriculoperitoneal (VP) shunt (controversial)
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- Disadvantages
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- Radiation
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- Time consuming
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- Normal study
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- 1 hour: Radiotracer reaches basal cisterns
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- 2-6 hours: Radiotracer reaches sylvian fissures
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- Trident sign: Activity in anterior interhemispheric fissure and sylvian fissures
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- 12 hours: Radiotracer reaches cerebral convexities
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- 24 hours: Radiotracer reaches superior sagittal sinus and is absorbed by arachnoid villi
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- No radiotracer activity should be seen in ventricles, although transient activity in ventricles at 4 hours is still considered normal
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- NPH
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- 24-48 hours: Ventricular activity is present, and no activity is seen in cerebral convexities
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- Heart configuration: Appearance of radiotracer activity in lateral ventricles on anterior view
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- Comma (also C-shaped) configuration: Appearance of radiotracer activity in lateral ventricles on lateral views
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- Butterfly configuration: Appearance of radiotracer activity in lateral ventricles on posterior view
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- Radiotracer activity in lateral ventricles at 24 hours or later is abnormal and consistent with diagnosis of NPH
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- Radiotracer activity not present in cerebral convexities by 24-72 hours is abnormal and suggestive of NPH
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- CSF movement patterns on cisternography
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- Type I: Radiotracer activity in cerebral convexities at 24 hours
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- Normal or noncommunicating hydrocephalus
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- Type II: Delayed activity in cerebral convexities at 24 hours without ventricular activity
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- Cerebral atrophy or aging
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- Type IIIa: Radiotracer activity in cerebral convexities at 24 hours with early transient ventricular activity
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- Indeterminate (can be seen with noncommunicating hydrocephalus, developing or resolving communicating hydrocephalus, or cerebral atrophy)
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- Type IIIb: No radiotracer activity in cerebral convexities at 24 hours with early transient ventricular activity
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- Suggestive of NPH (communicating hydrocephalus)
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- Type IV: No radiotracer activity in cerebral convexities at 24 hours with persistent ventricular activity
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- Suggestive of NPH (communicating hydrocephalus)
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- ## Other Modality Findings
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- MR
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- 1st-line imaging to diagnose NPH
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- Findings include ventriculomegaly out of proportion to sulcal enlargement, crowding of vertex sulci, acute callosal angle, enlarged sylvian fissures, hyperintense lesions in deep and periventricular white matter, flow void in cerebral aqueduct
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- Contraindications include hardware incompatible with MR and claustrophobia
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- CT
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- Shows ventriculomegaly out of proportion to sulcal enlargement and potentially additional MR findings
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- ## Imaging Recommendations
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- ### Best imaging tool
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- MR
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- Findings
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- Ventriculomegaly out of proportion to sulcal enlargement
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- Hyperintense lesions in deep and periventricular white matter
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- Flow void in cerebral aqueduct
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- 1st-line imaging to diagnose NPH
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- Advantages
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- No radiation to patient
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- Provides both anatomic and physiologic (CSF flow dynamics) information
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- Contraindications
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- Hardware incompatible with MR (cardiac pacemaker, aneurysm/embolization clips, prosthetic heart valves, etc.)
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- Claustrophobia
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- CT
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- Findings
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- Ventriculomegaly out of proportion to sulcal enlargement
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- Advantages
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- NECT can suggest diagnosis of NPH
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- Disadvantages
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- Radiation
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- No physiologic information
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- May be difficult to differentiate ventriculomegaly due to NPH from cerebral atrophy in setting of Alzheimer dementia or normal aging
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- ### Protocol advice
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- In-111 diethylenetriaminepentaacetic acid (DTPA) radionuclide cisternography
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- In-111 DTPA
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- Half-life (t1/2): 67 hours (2.8 days)
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- γ energies: 173 and 247 keV
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- Nonlipophilic
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- Not metabolized
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- Absorbed by arachnoid villi
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- Dosimetry
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- Spinal cord, brain, kidneys, bladder receive largest radiation dose
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- Patient preparation: Same as for any lumbar puncture (LP), except need radiotracer prepared ahead of time
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- Intrathecal injection of 0.5 mCi (18.5 MBq) In-111 DTPA
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- LP usually performed fluoroscopically by neuroradiologist, and radiotracer injected by nuclear medicine physician
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- Need appropriate cleanup and disposal of equipment due to radioactivity
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- Avoid contaminating patient's skin with radiotracer
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- Image acquisition
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- Planar &/or SPECT/CT with gamma camera
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- Low- or medium-energy, parallel hole collimator
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- Immediate anterior planar imaging to confirm intrathecal placement (bring portable gamma camera to LP suite or transport patient to nuclear medicine department)
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- 4-, 24-, and 48-hour (up to 72-hour) planar images of head: Anterior, posterior, both laterals
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- 24-hour SPECT/CT images of head if ventricular activity equivocal on planar imaging
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# DIFFERENTIAL DIAGNOSIS
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- [Alzheimer Dementia](/document/alzheimer-disease/2aad3ac4-44fd-43e5-8e50-a86987483af3)
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- Ventriculomegaly with sulcal enlargement
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- Small hippocampi
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- Type II or IIIa CSF flow pattern on cisternography
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- Dementia most pronounced clinical symptom
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- ## Parkinson Disease
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- Resting tremor (pill-rolling)
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- Shuffling gate
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- Cogwheel rigidity
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- ## Normal Aging
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- Type II CSF flow pattern on cisternography
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- ## Noncommunicating Hydrocephalus
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- Type I CSF flow pattern on cisternography
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- Usually diagnosed on MR
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# PATHOLOGY
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- ## General Features
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- ### Etiology
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- Causes
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- Idiopathic (50%)
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- Secondary (50%)
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- Subarachnoid hemorrhage or subdural hematoma
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- Meningitis or encephalitis
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- Leptomeningeal carcinomatosis
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- Head trauma
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- Brain radiation
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- Neurosurgery
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- Pathophysiology
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- Impaired CSF resorption by arachnoid villi causes communicating hydrocephalus
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- Traditional theory: Increased resistance to CSF outflow
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- Newer theory: Increased pulsations in intracranial pressure has been suggested as potential mechanism
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- Dysfunctional CSF dynamics without increase in intracranial pressure
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# CLINICAL ISSUES
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- ## Presentation
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- ### Most common signs/symptoms
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- Heterogeneous triad: Gait abnormality, urinary incontinence, dementia
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- All 3 present in only 10% of patients
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- Gait abnormality may manifest as magnetic gait, frontal ataxia, or gait apraxia (can be difficult to distinguish from shuffling gait or Parkinson disease)
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- Urinary urgency usually precedes incontinence
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- Dementia usually manifests with frontal lobe symptoms, such as apathy, lack of concentration and inattention, and psychomotor slowing
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- Symptom severity is related to CSF levels of neurofilament protein, marker of neuronal degeneration
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- ### Clinical profile
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- Reversible cause of dementia
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- ## Demographics
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- ### Age
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- Most common in patients > 60 years
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- Idiopathic form of NPH tends to present in older adults
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- Secondary NPH can present at earlier age
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- ### Sex
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- M = F
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- ## Natural History & Prognosis
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- Natural course: Continuing cognitive and motor decline, akinetic mutism, and eventual death
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- Potentially reversible cause of dementia when shunted, although gait symptoms are usually most predominant
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- Some patients worsen after shunting
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- ## Treatment
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- Ventricular shunt (most commonly VP)
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- Predictors of positive response to shunting
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- Patient < 75 years
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- Early symptoms (mild gait abnormality and urinary urgency)
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- Known history of intracranial infection or bleeding (nonidiopathic NPH)
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- Gait abnormality as dominant clinical symptom
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- Absence of central atrophy or ischemia
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- Prominent CSF flow void
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- Response to CSF removal trial
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- Exclusion of comorbidities, such as concomitant Alzheimer dementia or Parkinson disease
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- After shunt surgery
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- Variable outcome amongst studies, likely due to differing patient selection criteria
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- Early research may suggest role for amyloid, FDG, &/or DOPA PET in predicting outcomes to surgery
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# DIAGNOSTIC CHECKLIST
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- ## Consider
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- Whether ventricular dilation is solely due to atrophy or another underlying neurodegenerative disease
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- ## Image Interpretation Pearls
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- Classic finding of NPH on radionuclide cisternography
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- Prominent ventricular activity at 24 hours with absent activity over convexities
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