Nph

normal pressure hydrocephalus

1. Normal Pressure Hydrocephalus DR SANJOG CHANDANA

2. NPH Normal pressure hydrocephalus characteristically presents with progressive gait impairment, cognitive deficits, and urinary urgency and/or incontinence. potentially reversible cause of dementia   iNPH is a disorder of the elderly that characteristically presents with progressive gait impairment, cognitive deficits, and urinary urgency and/or incontinence ( Hakim-Adams triad - classically described by Colombian neurosurgeon Salomon Hakim and R D Adams in 1965).

3. There are two forms of normal pressure hydrocephalus: Idiopathic (primary) NPH - There is no identifiable cause. Symptomatic (secondary) NPH - Cases with risk factors of earlier brain infection, hemorrhage, traumatic brain injury, or radiation contributing to hydrocephalus fall into this category.  B oth are communicating types of hydrocephalus and both carry a similar prognosis. The significant difference between them is that secondary NPH affects persons of all ages, while iNPH is mainly a disease of the elderly . 

4. Epidemiology  0.2% among those in the age group 70 to 79 years and 5.9% of those 80 years of age (Sweden) average age of onset is approximately 70 years, and men and women are affected in equal numbers. In some studies M:F= 2:1. 6% of all cases of dementia Incidence : 0.2 to 5.5 per 100000 person-years,

5. Pathophysiology The hyperdynamic flow of cerebrospinal fluid (CSF) in the aqueduct Reduced compliance of the subarachnoid space Increased CSF pulse pressure Reduced reabsorption of CSF in the venous system due to increased resistance Reabsorption of CSF through abnormal mechanisms like transependymal flow, rather than through Pacchionian granulations Cerebral blood flow reduction

6. Pathophysiology Altered expression of cerebrospinal fluid (CSF) tumor necrosis factor-alpha (which is known to regulate CSF production) and transforming growth factor-beta Failure of drainage of vasoactive metabolites (Silverberg 2004) - Abnormalities in CSF production and turnover may lead to a failed clearance of toxic molecules - an inability to clear amyloid-b peptides and tau protein could lead to an increase in their concentration in brain interstitial fluid, creating a potentially hostile environment for neuronal function and survival

7. Pathophysiology Loss of the Windkessel effect in the skull base arteries – The imbalance of CSF production and resorption is not due to overproduction but because of increased resistance to CSF outflow.  The loss of elasticity of blood vessels may be either primary due to atherosclerosis or secondary due to low craniospinal compliance impeding the expansion of the skull base arteries. The increased brain pulsations result in higher compressive stress and shearing forces in the cerebral parenchyma.

8. Pathophysiology Due to the physical and physiological differences between superficial and deep (periventricular) brain tissue, the damage and loss start mainly in the periventricular areas as a result of cerebral auto-compression. This focal brain damage manifests as ventriculomegaly. The loss of the Windkessel effect also results in the lowering of cerebral blood flow, which leads to the simultaneous occurrence of iNPH and cerebral hypoperfusion; the latter, in turn, lowering CSF turnover.

9. Causes of gait abnormality: The increased intracranial pressure leads to stretching and compression of the fibers of the corticospinal tract in the corona radiata that supply the legs, which pass in the close vicinity to the lateral ventricles as a result of interstitial edema Poor perfusion of periventricular white matter and prefrontal regions Compression of brainstem structures , such as the pedunculopontine nucleus

10. Cause of dementia: As the ventricles continue to enlarge and the cortex pushes against the inner table of the calvarium, radial shearing forces lead to dementia .

11. Cause of bladder incontinence At an early stage, -the periventricular sacral fibers of the corticospinal tract are stretched causing a loss of voluntary (supraspinal) control of bladder contractions (Gleason 1993) I n later stages of the disease, dementia may contribute to incontinence ( Corkill 1999).

12. C /F The complete Hakim triad is seen in 50% to 75% of patients, with gait and cognitive disturbances occurring in 80% to 95%, and urinary incontinence in 50% to 75% of patients. The International Society for Hydrocephalus and Cerebrospinal Fluid Disorders guidelines define “ probable NPH ” by the combination of insidious onset gait dysfunction after 40 years old without precipitating events, lasting at least 3 to 6 months , in the absence of comorbidities which could fully explain the symptoms

13. Gait disturbance F irst and most common symptom to appear and also the first one to resolve postoperatively. O ccurrence of gait abnormality before the onset of cognitive decline has been reported to predict a better prognosis after shunting. “ shuffling,” “magnetic,” and “wide-based.” finally becoming broad-based, slow, short-stepped, and glue-footed

14. Gait disturbance External rotation in foot posture Poor foot clearance (festination, shuffling, tripping) Notable difficulty turning on the body’s long axis (multistep turns)  Gait initiation failure or freezing of gait worse with the eyes closed tremor in the extremities, which is present in 40% of iNPH patients, does not respond to shunt surgery. 

15. Urinary frequency/incontinence: The bladder symptoms are due to detrusor overactivity, which can cause increased frequency and urgency of micturition or frank incontinence.

16. Dementia: Subcortical type and characteristically presents with I nertia, forgetfulness, and poor executive function . E arliest cognitive signs of iNPH include psychomotor retardation , reduced attention as well as executive and visuospatial dysfunction occurring due to frontal and subcortical dysfunction

17. Investigations CT MRI FIESTA

18. Evans index: It is a frontal horn ratio defined as the maximal frontal horn ventricular width divided by the transverse inner diameter of the skull; it signifies ventricular enlargement if it is greater than or equal to 0.3.

19. Callosal angle: This angle should be between 40 to 90 degrees in patients with iNPH .

20. B ulging of the lateral ventricular roof (upward bowing and stretching of the corpus callosum).

21. CSF flow study: the flow rate of greater than 24.5 mL/min is 95% specific for NPH.  Aqueductal flow void seen in T2 weighted images due to increased CSF flow velocity is not a useful sign.

22. Disproportionately enlarged temporal horns of the lateral ventricles with relatively normal sulcal size.

23. Tests of CSF drainage increase the diagnosis and the prognostic accuracy above 80%: Spinal tap test: Lumbar puncture removing of 30 to 70 mL of CSF, which is repeatable on two or three consecutive days. There is continuous subarachnoid drainage from the lumbar spine of 150 to 200 mL of CSF daily for 2 to 7 days. It has high sensitivity (50 to 100%) and high positive predictive value (80 to 100%).

24. These tests are considered to be positive if the number of steps the patient takes in a 10-meter gait test, and the time needed to walk 10 meters, are reduced by not less than 20%, and/or psychometric testing shows an improvement of at least 10%.

25. Nuclear medicine studies: Some of the non-specific signs seen in iNPH are: The heart-shaped appearance of lateral ventricles (normally shaped like a trident) persistence of tracer more than 24 to 48 hours in the ventricular system due to impaired absorption An absence of an extension of tracer onto the superior aspect of lateral ventricles Backflow of CSF into lateral ventricles

26. Management Conservative – Watchfulness ( uncertain diagnosi ) Surgical : Shunting : VP Shunt , VA shunt , LP shunt.

27. Factors suggesting favorable outcome following shunt surgery: Aqueductal stroke volume greater than 42 microliters Lack of white matter lesions on MRI B-waves longer than 50% of intracranial pressure monitoring time Resistance to CSF outflow over 18 mmHg

28. Factors suggesting unfavorable outcome following shunt surgery: Severe dementia Dementia as a presenting symptom MRI abnormalities, cerebral atrophy, and multiple white matter lesions Misdiagnosis and delayed recognition