NPH NORMAL PRESSURE HYDROCEPHALUS Adams & Hakim syndrome: symptomatic occult hydrocephalus with 'normal' CSF pressure 1965 Communicating hydrocephalus Pathophysiology: Despite advances in the diagnosis and management of this condition, the exact pathogenesis of NPH remains uncertain. --the ventricles expand at the expense of brain volume, causing both brain compression and periventricular white matter changes --B waves particularly in REM Clinical symptoms result from distortion of the central portion of the corona radiata by the distended ventricles. This may also lead to interstitial edema of the white matter and impaired blood flow, as suggested in nuclear imaging studies. The periventricular white matter anatomically includes the sacral motor fibers that innervate the legs and the bladder, thus explaining the abnormal gait and incontinence. Compression of the brainstem structures (ie, pedunculopontine nucleus) could also be responsible for gait dysfunction, particularly the freezing of gait that has been well described. Dementia results from distortion of the periventricular limbic system. Normal pressure hydrocephalus may begin with a transient high-pressure hydrocephalus with subsequent ventricular enlargement. With further enlargement of the ventricles, CSF pressure returns to normal; Medscape:Author: Arif I Dalvi, MD; Chief Editor: Selim R Benbadis, MD Epidemiology: Age usually > 60 yrs Slight male preponderance. The prevalence of NPH may be as high as 14% in extended care facility patients. Race & Sex are not associated with the development of NPH. Clinical findings: Triad: Gait Disturbance Urinary Incontinence Cognitive Impairment - The Triad is not pathognomonic Other symptoms: -Psychiatric disturbances: depression, bipolar disorder, paranoia, aggressiveness -11% identical to those of idiopathic parkinsonism Infrequently: -SIADH, syncope, Symptoms not expected with NPH ( solely as a result of NPH ): -papilledema, seizures (prior to shunting),headaches Etiology: Idiopathic Secondary : delayed ( many years ) Trauma SAH Meningitis intracranial surgery (esp. posterior fossa surgery ) Tumors ( including carcinomatous meningitis ) Deficiency of the arachnoid granulations in about 15% of patients with Alzheimer's disease (AD) Gait Disturbances: most common initial symptom and occurs in almost 90% of patient Common initial symptoms include: unsteadiness, recurrent falls, shuffling, and reduced walking speed More advanced symptoms include: difficulty initiating gait and imbalance on turning. MAGNETIC gait ( glued to the floor ): broad base and slow, small steps with reduced height clearance Patients may have disturbances in stance with a tendency to lean forward and imbalance exacerbated by eye closure. absence of weakness or dysdiadochokinesis. END-stage phase: pyramidal tract damage that cannot be reversed by surgery DDX: -UMN: cervical myelopathy -lower limb weakness: canal stenosis -Parkinson: * is not wide-based * other hallmarks: tremor, lead pipe rigidity, mask-liked face * NPH tend to mobilize with a relatively preserved arm swing. * NPH has gait apraxia that does not respond to external cueing such as counting Urinary incontinence: may be a separate symptom or may be a consequence of gait disturbance or cognitive impairment. Frequency & Urgency thought to be due to involvement of the sacral fibers of the CS tract. May be change or worsening of urinary symptom. in a study by Sakakibara and colleagues, 95% of patients had urodynamic parameters consistent with detrusor overactivity. Cognitive Impairment: < 5% of all case of dementia primarily memory impairment with bradyphrenia (slowness of thought) & bradykinesia memory loss, reduced attention, difficulty planning, slowness in thought, apathy and inertia. subcortical frontal dysexecutive syndrome: impairment of multistep procedure,insight,decision making,task switching true aphasia is unusual Speech disturbance: executive dysfunction or motivational problems. DDx.: -AD: cortical deficit: aphasia, apraxia,agnosia -Binswanger's disease: * most difficult DDx. * a form of subcortical vascular encephalopathy. * predominantly frontal cognitive deterioration. * gait disturbance: ataxia or motor dysfunction, or both. * similar MRI features. * FND may be present. Binswanger disease or small vessel dementia - Subcortical arteriosclerotic encephalopathy (SAE) - progressive neurological disorder caused by arteriosclerosis and thromboembolism affecting the blood vessels that supply the white-matter and deep structures of the brain (basal ganglia and thalamus). - MRI changes are much more striking, consisting of subcortical and periventricular lesions visible on FLAIR, T2-weighted, and proton-density sequences. The areas are irregular, commonly grouped around the frontal and occipital horns, and in the centrum semi ovale. Moderate, generalised cerebral atrophy is invariably present, and lacunar infarcts in the basal ganglia and thalami are common - BD is a progressive disease; there is no cure Neuro-radiologic features: CT or MRI is required to establish the diagnosis of NPH: obstruction, atrophy, CVA, congenital enlargement Hydrocephaly: ventriculomegally + one of the supportive features Ventriculomegaly: -Evans Index: >0.3 -Bicaudate ratio: >= 0.25 Supportive features: - enlargement of the temporal horns of the lateral ventricles not entirely attributable to hippocampus atrophy. - callosal angle >= 40 degree - evidence of altered brain water content, including periventricular signal changes not attributable to microvascular ischemic changes or demyelination. * PVL: hypodensity in CT or hyperintensity in T2 MRI - aqueductal or fourth ventricular flow void on MRI. Prominent flow void in the aqueduct and third ventricle, the so-called jet sign, (presents as a dark aqueduct and third ventricle on a T2-weighted image where remainder of CSF is bright) MRI (T2) Note the very prominent flow void in the aqueduct. Callosal angle: - Ideally the angle should be measured on a coronal image perpendicular to the anterior commissure -posterior commissure (AC-PC) plane at the level of the posterior commissure - In general patients with NPH have smaller angles than those with ventriculomegaly from atrophy or normal controls - A normal values is typically between . In patients with NPH that values is lower, between 50-80 Callosal angle Other supportive imaging findings but not required: - previous brain imaging - cine MRI : increase in ventricular flow rate -radio-nuclide cisternogram -SPECT acetazolamide challenge : decrease in periventricular perfusion that is not altered by acetazolamide. The acetazolamide challenge test, which normally increases CBF, fails to do so in NPH patients, particularly in the periventricular white matter. This lack of the usual vasomotor response to carbonic anhydrase inhibitors (or to inhaled CO2) probably indicates that the arterioles are already maximally dilated as a result of local ischemia (http://www.ajnr.org) Features that correlate with favorable response to shunt: - periventricular low density on CT or high intensity on T2WI MRl - compression of convexity sulci (focal sulcal dilation may sometimes be seen and may represent atypical reservoirs of CSF which may diminish after shunting and should not be considered as atrophy) - rounding of the frontal horns Supplementary Prognostic Testing: Lumbar puncture tap test External lumbar drainage Measures of CSF outflow resistance LP (tap test): -normal LP opening pressure(OP) in left lateral decubitus: * cmH20 * should be 24 cmH2O suggests non-communicating hydrocephalus ) -NPH: * average OP is cmH2O with upper limit of 24 cmH2O * patients with an initial OP>10 cmH2O have higher response rate to shunt **Normal CSF pressure range (5 to 18 mmHg / 7 to 24 cmH2O) and that no biochemical or microbiologic abnormalities are present Method : 40 50 cc of CSF withdrawn - send to RLT - specificity of 100% with a sensitivity of 26% - Symptomatic improvement after removal of CSF has a high positive predictive value (73% to 100%) of a probably favorable outcome with shunt placement. - remembered that improvement after a shunt is often delayed in many patients, so a simple tap test would not be expected to reveal all patients who might benefit from a shunt. - low sensitivity of the "tap test" precludes using this method as a diagnostic tool for exclusion. Ambulatory Lumbar Drainage: Drip chamber: -ear if recumbent & shoulder if sitting or ambulating. Proper function : 300cc CSF/day. A 5 day trial (mean time to improvement: 3 days). sensitivity (50% to 80%), specificity (80%) Improved symptoms : PPV (80% to 100%) Disadvantages: - inpatient stay - complications: * nerve root irritation: withdrawn several millimeters. * hemorrhage * CSF infection Measurement of CSF outflow resistance: - reflect the CSF absorption pathways (conductance & impedance ). - injection into a CSF space (e.g., ventricles or lumbar sac) either by bolus or infusion. - specificity of 87%, a sensitivity of 46%, PPV (75% to 92%). - can be use as a method of comparing CSF hydrodynamic before & after shunt Other supplementary tests: CBF measurement: - no specific findings & predicting response - increase in CBF after shunting correlates with clinical improvements EEG: -no specific findings Direct ICP measurement: - exclude other more acute causes of Hydrocephalus - no prognostic value Dignosis: Treatment: Managements before surgery: - in probable NPH, w/o further testing, the degree of certainty of the Dx of NPH is 50-60%. - to increase the certainty of response to shunting, one or more of the following tests is recommended: * external lumbar drainage * resistance test * tap test: - neg. test dose not R/O possibility of responsing ( supplement tests required ) - OP>24 cmH2O : search for other causes ( does not R/O shunting as Tx ) Medication: - No definitive evidence exists that medication can successfully treat NPH. - In patients who are poor candidates for shunt surgery, however, repeated lumbar punctures in combination with acetazolamide may be considered. Surgery (CSF diversion procedures): - Ventriculoperitoneal shunt (VPS ): procedure of choice - Lumboperitoneal shunt - Endoscopic 3 rd ventriculostomy (ETV): nonvalidated outcome measures & not be considered as 1 st line of Tx in most cases VPS: - Medium pressure valve. (closing pressure mm H2O): use for most cases - Low-pressure valve: response rate may be higher ( risk of SDH) - programmable shunt valve: set initially at a high pressure (to reduce risk of subdural hematoma) and gradually decreasing the pressure setting over a number of weeks F/U : clinically & CT: for about 6-12 months Patients who do not improve and whose ventricles do not change: R/O shunt malfunction, If not obstructed, a lower pressure valve or a lower pressure selected on a programmable shunt Complications of shunting for NPH: - as high as 35% ( due to the frailty of the elderly brain ) - potential complications: * infection * seizure * obstruction / disconnection * subdural hematoma / hygroma SDH: - higher risk with low pressure valve and older patients. - Usually accompanied by headache. - most resolve spontaneously or remain stable. - one third require evacuation and tying off of shunt (temporarily or permanently). - reduces by : * Gradually sit patient up over a period of several days; proceed more slowly in patients who develop low-pressure headache * use of a programmable shunt valve OUTCOME: - improvement of symptoms: incontinence, then gait disturbance & lastly cognitive impairment - Some responders may subsequently deteriorate: Shunt malfunction and subdural collections must be ruled out before ascribing this to the natural course of the condition. markers of good response to shunting: * LP :. OP > 100 mmH2O * CT MRI * cisternogram :. delayed clearance of the radiotracer over the cerebral convexities after 48 to 72 hours ( 75% chance for shunt responce) * continuous CSF recording :. pressure > 180 mmH2O / frequent B waves * clinical:.when symptoms present for a shorter time.presence of classic triad.gait disturbance as the primary symptom * Normal-sized or occluded sylvian fissures and cortical sulci on CT or MRI * Absent or moderate white matter lesions on MRI * Presence of a clearly identified etiology DDx: Thank you