Normal Pressure Hydrocephalus ( NPH )

1. Normal Pressure Hydrocephalus (NPH) Date: 2005/09/27 Speaker: Int. 吳忠泰 Supervisor: V.S. 俞芹英

2. Outlines • Definition • Epidemiology and etiology • Physiology and pathophysiology • Diagnosis and differential diagnosis • Treatment and complication • Prognosis

3. Definition • First described in 1965 by Hakim and Adams • Normal CSF pressure • Ventriculomegaly • Clinical triad: • Slowly progressive gait disorder • Impairment of mental function • Sphincteric incontinence

4. Epidemiology • 1 per 25’000 • Accounts for approximately 0.5-5% (up to 6%) of dementias • One of the few treatable causes of dementia • Most common in patient > 60 y/o • M > F

5. Etiology • Idiopathic: Elderly, unknown cause, 50% of NPH • With a preceding cause: Young • Subarachnoid hemorrhage (SAH) • Trauma • Meningitis (TB, syphilitic, etc.) • Surgery, irradiation • Storage disease (mucopolysaccharidosis)

6. Physiology of CSF Flow

7. Pathophysiology of Hydrocephalus Communicating hydrocephalus Obstructive hydrocephalus

8. Pathophysiology of NPH Incontinence Enlarged lateral ventricles Gait disturbance Dementia

9. Pathophysiology of NPH • On the basis of both dynamic and ischemic factors • Ventricular enlargement • Vascular stretching → Ischemia • Decreased compliance of ventricular wall • High pulse pressure • Barotrauma or shearing stress

10. Dynamics of NPH • Transmantle pressure gradient • Difference in pressure between ventricle and subarachnoid space • Gradient ↑ temporarily → Ventricle↑ • B wave (plateau) • Transient elevations of mean and pulse pressure • Water-hammer effect→ Ventricle↑ • More than 50% of time

11. Dynamics of NPH • Aqueductal CSF flow void • Increased CSF flow velocity • Favorable response to CSF diversion • Aqueductal CSF stroke volume • CSF pulsating back and forth through the aqueduct during systole and diastole • Favorable response to shunting • Hyperdynamic CSF flow

12. Dynamics of NPH • Saline infusion test • CSF resorption in NPH is abnormal • Arachnoid granulation? Arachnoidal villi? • Venous compromise • Increased transvenular resistance in superior saggital sinus cause NPH • What cause venous compromise? Microangiopathy? Deep white matter ischemia?

13. Ischemia of NPH • Acetazolamide challenge test • Cerebral blood flow (CBF)↑ in normal person • Failed to cause CBF↑ in NPH p’t • Indicate the arterioles are already maximally dilated because of ischemia • CSF diversion → CBF improve and response to acetazolamide

14. Ischemia of NPH • Compensatory CSF flow • Periventricular white matter • Increased interstitial fluid • Loss of parenchymal compliance

15. Pathophysiology of NPH • Dynamic • Hyperdynamic CSF flow • Impaired CSF resorption • Ischemic • Reduced CBF • Periventricular white matter lesion

16. Diagnosis • Clinical symptoms and signs • Gait disturbance • Dementia • Urinary incontinence • The moment when highly suspect NPH !! • Image • MRI (T2WI) with CSF flow study • CT with lumbar puncture

17. Image Findings - CT • Ventriculomegaly • Sulcal atrophy • Ventriculosulcal disproportion • Can DDx with other dementia syndromes

18. Image Findings - CT • Rounded frontal and temporal horns • Periventricular lucency • Transependymal CSF flow • Corpus callosum thinning

19. Image Findings - MR • The same as CT • Temporal horn out of proprotion to hippocampal atrophy • Corpus callosum bowed upward

20. Image Findings - MR • Periventricular lesions in T2WI • Transependymal CSF flow • Deep white matter damage

21. Image Findings - MR • Aqueductal flow void sign • Jet sign • A jet of turbulent CSF flow on the distal aqueduct • Predictive of shunt responsiveness

22. Image Studies - MR • CSF flow study • Aqueductal stroke volume • Increased velocity (hyperdynamic flow) • VV/ICV ratio • VV/ICV ratio > 30% (in 13 of 14 pts) (VV: ventricular volume; ICV: intracranial CSF space volume) • MRS • Intraventricular lactate peaks (ischemia)

23. Differential Diagnosis • Dementia syndromes • Alzheimer’s disease • Hydrocephalus ex vacuo • Intraventricular lactate • Parkinsonism • Parkinson’s disease • Periventricular leukomalacia

24. Treatment • Surgical shunting • VP shunt • Lumbar puncture • Miller Fisher test: Gait assessment before and after 30mL CSF drainage (high rate of false negative) • Continuous CSF drainage of 200 mL per day for 3-5 days

25. Complications of shunt • Infection: S. aureus, S. epidermidis • Subdural hematoma • Shunt obstruction • Low pressure state • Epilepsy • Pneumocephalus • Ascites

26. Prognosis • Response rate for shunt • 50-70% with known preceding cause • 30% with idiopathic group • Non-selective patient • 1/3 improve, 1/3 arrest, 1/3 deteriorate

27. Prognosis • Positive response to shunting: • Absence of central atrophy or ischemia • Gait apraxia as dominant symptoms • Prominent CSF flow void (stroke volume > 42 mL) • Known history of cause (nonidiopathic type)

28. References • Raymond D. Adams, Maurice Victor. Principles of Neurology, 5th edition: 545-6 • Roger N. Rosenberg et al. The Clinical Neuroscience – Neurology/ Neurosurgery: 1205-19 • Kenneth W. Lindsay, Ian Bone. Neurology and Neurosurgery Illustrated, 4th edition: 128-9, 370-3 • Anne G. Osborn et al. Pocket Radiologist – Brain Top 100 Diagnosis: 228-30 • William G. Bradley. Normal Pressure Hydrocephalus: New Concepts on Etiology and Diagnosis. AJNR 2000; 21: 1586-90 • eMedicine: http://www.emedicine.com/neuro/topic277.htm http://www.emedicine.com/radio/topic479.htm

29. Thanks for Your Attendance…