Management of normal pressure hydrocephalus

Author: Meg Verrees, Warren R. Selman
Date: Sept 15, 2004

The diagnosis of normal pressure hydrocephalus (NPH) depends on symptom profile, presence of radiographic features, and the outcome of diagnostic tests. Although numerous techniques are used to identify patients who are likely to have NPH and various means are used to identify those patients most likely to respond to treatment, no definitive method exists to prove diagnosis. Cerebrospinal fluid (CSF) diversion accomplished via placement of a ventriculoperitoneal shunt is the most common treatment.

The precise incidence of NPH is hard to determine, because the condition lacks a formal, consensus-based definition. Some physicians base the diagnosis strongly on radiographic evidence; another group of health care professionals relies more on clinical indications, and still others use a combination of signs and symptoms that they have found to be reliable. A rare cause of dementia, NPH primarily affects persons older than 60 years and is estimated to be the source of dementia in 5 percent or less of affected persons. (1-3)

Background

Formed by specialized tufts of capillaries called choroid plexus at a rate of approximately 20 mL per hour, CSF circulates from dual paired lateral ventricles through paired foramina of Monro into a single midline third ventricle (Figure 1). From this midline cavity, CSF continues through the aqueduct of Sylvius into the fourth ventricle, situated within the posterior fossa. CSF exits the ventricular system via three small apertures to pass into the subarachnoid space. CSF contained within the subarachnoid space envelops and cushions the brain and spine. At any one time, 140 mL of CSF is contained within the neuroaxis; approximately 25 mL is contained within the ventricles while the majority is transiently sequestered within cisternae situated at the base of the brain or within spaces surrounding the cerebral convexities and the spinal cord. Within the subarachnoid space, CSF is absorbed by arachnoid granulations positioned near the top of the brain. These conduits of CSF outflow drain into the venous system via the superior sagittal sinus. (2,4)

[FIGURE 1 OMITTED]

NPH is a disorder of decreased CSF absorption, not excess formation. (4) Whether from an established or unknown cause, the arachnoid granulations fail to maintain their baseline removal of CSF, often secondary to fibrosis and scarring that obscure absorptive interfaces. A pressure gradient develops between the fluid in the subarachnoid space surrounding the brain and the ventricular system. The differential pressures eventually lead to decreased CSF production and the setting of a higher, yet still normal, baseline pressure. (1) This new pressure distends the ventricles, stretching surrounding nerve fibers and compressing the periventricular parenchyma. This encroachment on brain tissue by enlarged ventricles impinges on the caliber of arterioles and capillaries, often resulting in ischemia. (2)

The theory that implicates fibrosis as the pathophysiologic basis of NPH is not uncontested. Some sources believe that idiopathic NPH is a persistence of poor drainage of CSF originating in childhood as benign external hydrocephalus secondary to insufficient removal of CSF by immature arachnoid granulations. (5,6) Additionally, agreement about whether NPH is an entity consisting of normal, or near normal, pressure remains far from unanimous because some physicians feel that symptoms may be the result of intermittent spikes of high pressure known as B waves. (1,7-10)

Regardless of the originating cause, a communicating hydrocephalus is produced. This type of hydrocephalus, in contrast to non-communicating hydrocephalus, indicates the absence of an obstructive mass, such as a tumor, abscess, or blood clot, infringing on the central pathway of CSF flow.

The inciting etiology of NPH may be recognized or unknown. Subarachnoid hemorrhage, head injury, and meningitis are frequently implicated preceding events. (3,4) Patients with established etiology of NPH tend to respond more favorably to shunting than patients with chronic idiopathic hydrocephalus. (3,5,11-13)

Signs and Symptoms

The triad of gait instability, urinary incontinence, and dementia distinguishes NPH (4,14-16) (Table 1). Elucidation of the presence of these three symptoms, as well as their predominance and pattern of presentation, is essential. One study (2) reported a 65 percent positive predictive value of this classic constellation in selecting patients for ventriculoperitoneal shunting. Although NPH commonly is referred to as a treatable form of dementia, cognitive deficits and memory loss are the symptoms least specifically indicative of this syndrome and the last to respond to shunting. (15,17,18) Gait instability is most often the first presenting and most significant problem. (7,12,16,19,20) In a review (20) of 35 studies evaluating diagnostic studies and outcomes of patients with NPH, investigators arrived at a similar conclusion. The aberrant pattern of ambulation often is composed of a slow gait; short, shuffling steps; and a wide-based stance. (4,15,21)

The term "gait apraxia" is sometimes used to describe the problem with locomotion experienced in patients with NPH. This phrase entails difficulty in sequencing the individual components that constitute ambulation (i.e., strike, stance, and swing), as well as a struggle to coordinate alterations in course or fluid continuity of movement. Indeed, trouble with initiation of ambulation, imbalance during action and standing, as well as frequent falls, are observed. (7) In one study, (16) 10 patients with NPH were compared with 12 healthy, age-matched control patients; the patients with NPH were found to have a slower gait, shorter stride, and imbalance offset by a wide stance.

Urinary incontinence usually follows gait abnormalities and almost always includes urinary urgency. (1,2,22) Deformation of periventricular corticospinal tract sacral nerve fibers seems to be the likely reason for incontinence. (4) Ineffective contraction of the detrusor muscle is identified on urodynamic studies. (4)

Dementia usually is not the presenting or most overt symptom of NPH. (18) It is often, although not invariably, evident. (1,4) If present, cognitive impairment should be of the subcortical type. Inattention, latency in recall, and lack of spontaneity frequently are encountered indicators of subcortical dementia, the intellectual impairment observed in NPH. (4) An answer provided by a patient suffering from NPH is frequently correct; a fact recalled is most often accurate. (1) These features distinguish the dementia of NPH from the cognitive decline noted in patients with Alzheimer's disease. (12) NPH dementia should not include difficulty with word formation, trouble interpreting stimuli within appropriate context, or inability to sequentially carry out simple tasks, which characterize aphasia, agnosia, or apraxia and are more indicative of cortical dementias. The physiologic cause of the dementia intermittently associated with NPH remains to be determined positively, although deformation of limbic structures surrounding the enlarged ventricles has been suggested. (4)

Ultimately, identifying patients with NPH involves the careful weighing of likelihoods. The time to refer patients to a subspecialist (i.e., neurologist or neurosurgeon) for a more involved and specific work-up and confirmation or contradiction of suspicion is when even a slight chance of the diagnosis arises or when just a loose grouping of the triad is encountered. Early referral, when NPH is suspected, is optimal to identify the greatest number of patients actually experiencing this disorder and to offer timely treatment to those who are most likely to respond to intervention. Expedient differentiation of NPH from other diagnoses, some of which are life-threatening, as well as directly and conclusively treated, also is imperative (Table 2).

Radiographic Features

Imaging is essential in patients presenting with signs and symptoms of NPH to confirm the absence of subdural hematoma, infection, neoplasia, or other structural abnormality. Compared with studies of normal patients (Figure 2a), magnetic resonance imaging (MRI) of patients who have NPH demonstrates ventriculomegaly with maintained cerebral parenchyma (Figure 2b). This finding is in contrast to the ventricular dilation associated with significant loss of brain tissue evident in images of patients who have Alzheimer's disease (Figure 2c). Additionally, MRIs of patients who have Alzheimer's disease frequently reveal focal loss of tissue in the hippocampus. (1) In patients with NPH, the volume of medial temporal lobe tissue should be maintained. (1)

[FIGURE 2 OMITTED]

TABLE 1Signs and Symptoms of NormalPressure HydrocephalusAmbulation Difficulty or arrest in initiation of ambulation Feet appear "glued to the floor" Gait instability, multiple falls Wide-based stance, shuffling stepsGeneral Generalized slow movementIncontinenceMentation Lack of spontaneity in movement, verbal response, and emotion Latency in response to questions or reaction to situations Slowness in processing informationTABLE 2Differential Diagnosis of Normal Pressure HydrocephalusAlzheimer's diseaseCarcinomatous meningitisChronic alcoholismCombinations of conditions affecting gait (e.g., rheumatoid arthritis, cervical stenosis) coupled with conditions that impinge on mentation (e.g., Alzheimer's disease, multi-infarct dementia) and those that have an effect on urination (e.g., prostate disease)Intracranial infection (e.g., abscess, subdural empyema, meningitis)Multi-infarct dementiaParkinson's diseaseSubcortical arteriosclerotic diseaseSubdural hematomaSystemic diseases (e.g., hypothyroidism, Addison's disease) or malignancyTumor (benign or malignant)Strength of RecommendationsKey clinical recommendation Label ReferencesExamination of the results of multiple B 2,20 studies yields a wide variation in patient response to shunting.No gold standard test is available to B 3,7,8 identify patients who will benefit from the shunting procedure.

REFERENCES

(1.) Vanneste JA. Diagnosis and management of normal-pressure hydrocephalus. J Neurol 2000;247:5-14.

(2.) Vanneste JA, Augustijn P, Dirven C, Tan WF, Goedhart ZD. Shunting normal-pressure hydrocephalus: do the benefits outweigh the risks? A multicenter study and literature review. Neurology 1992;42:54-9.

(3.) Vanneste J, Augustijn P, Tan WF, Dirven C. Shunting normal pressure hydrocephalus: the predictive value of combined clinical and CT data. J Neurol Neurosurg Psychiatry 1993;56:251-6.

(4.) Gleason PL, Black PM, Matsumae M. The neurobiology of normal pressure hydrocephalus. Neurosurg Clin North Am 1993;4:667-75.

(5.) Bradley WG. Normal pressure hydrocephalus: new concepts on etiology and diagnosis. AJNR Am J Neuroradiol 2000;21:1586-90.

(6.) Bradley WG. Cerebrospinal fluid dynamics and shunt responsiveness in patients with normal-pressure hydrocephalus [Letter]. Mayo Clin Proc 2002;77:507-8.

(7.) Savolainen S, Hurskainen H, Paljarvi L, Alafuzoff I, Vapalahti M. Five-year outcome of normal pressure hydrocephalus with or without a shunt: predictive value of the clinical signs, neuropsychological evaluation and infusion test. Acta Neurochir (Wien) 2002;144:515-23.

(8.) Pisani R, Mazzone P, Cocito L. Continuous lumbar cerebrospinal fluid pressure monitoring in idiopathic normal-pressure hydrocephalus: predictive value in the selection for shunt surgery. Clin Neurol Neurosurg 1998;100:160-2.

(9.) Symon L, Dorsch NW, Stephens RJ. Pressure waves in so-called low-pressure hydrocephalus. Lancet 1972;2(7790):1291-2.

(10.) Symon L, Dorsch NW. Use of long-term intracranial pressure measurement to assess hydrocephalic patients prior to shunt surgery. J Neurosurg 1975;42:258-73.

(11.) Black PM, Ojemann RG, Tzouras A. CSF shunts for dementia, incontinence, and gait disturbance. Clin Neurosurg 1985;32:632-51.

(12.) Bret P, Guyotat J, Chazal J. Is normal pressure hydrocephalus a valid concept in 2002? A reappraisal in five questions and proposal for a new designation of the syndrome as "chronic hydrocephalus." J Neurol Neurosurg Psychiatry 2002;73:9-12.

(13.) Vanneste JA. Three decades of normal pressure hydrocephalus: are we wiser now? J Neurol Neurosurg Psychiatry 1994;57:1021-5.

(14.) Hakim CA, Hakim R, Hakim S. Normal-pressure hydrocephalus. Neurosurg Clin North Am 2001;12:761-73.

(15.) Krauss JK, Faist M, Schubert M, Borremans JJ, Lucking CH, Berger W. Evaluation of gait in normal pressure hydrocephalus before and after shunting. Adv Neurol 2001;87:301-10.

(16.) Stolze H, Kuhtz-Buschbeck JP, Drucke H, Johnk K, Diercks C, Palmie S, et al. Gait analysis in idiopathic normal pressure hydrocephalus--which parameters respond to the CSF tap test? Clin Neurophysiol 2000;111:1678-86.

(17.) Black PM. Idiopathic normal-pressure hydrocephalus. Results of shunting in 62 patients. J Neurosurg 1980;52:371-7.

(18.) Petersen RC, Mokri B, Laws ER Jr. Surgical treatment of idiopathic hydrocephalus in elderly patients. Neurology 1985;35:307-11.

(19.) Meier U, Zeilinger FS, Kintzel D. Signs, symptoms and course of normal pressure hydrocephalus in comparison with cerebral atrophy. Acta Neurochir (Wien) 1999;141:1039-48.

(20.) Hebb AO, Cusimano MD. Idiopathic normal pressure hydrocephalus: a systematic review of diagnosis and outcome. Neurosurgery 2001;49:1166-84.

(21.) Fisher CM. The clinical picture in occult hydrocephalus. Clin Neurosurg 1977;24:270-84.

(22.) Larsson A, Wikkelso C, Bilting M, Stephensen H. Clinical parameters in 74 consecutive patients shunt operated for normal pressure hydrocephalus. Acta Neurol Scand 1991;84:475-82.

(23.) Bradley WG Jr, Scalzo D, Queralt J, Nitz WN, Atkinson DJ, Wong P. Normal-pressure hydrocephalus: evaluation with cerebrospinal fluid flow measurements at MR imaging. Radiology 1996;198:523-9.

(24.) Hurley RA, Bradley WG Jr, Latifi HT, Taber KH. Normal pressure hydrocephalus: significance of MRI in a potentially treatable dementia. J Neuropsychiatry Clin Neurosci 1999;11:297-300.

(25.) Mase M, Yamada K, Banno T, Miyachi T, Ohara S, Matsumoto T. Quantitative analysis of CSF flow dynamics using MRI in normal pressure hydrocephalus. Acta Neurochir Suppl (Wien) 1998;71:350-3.

(26.) Mori K. Management of idiopathic normal-pressure hydrocephalus: a multiinstitutional study conducted in Japan. J Neurosurg 2001;95:970-3.

(27.) Chen IH, Huang CI, Liu HC, Chen KK. Effectiveness of shunting in patients with normal pressure hydrocephalus predicted by temporary, controlled-resistance, continuous lumbar drainage: a pilot study. J Neurol Neurosurg Psychiatry 1994;57:1430-2.

(28.) Haan J, Thomeer RT. Predictive value of temporary external lumbar drainage in normal pressure hydrocephalus. Neurosurgery 1988;22:388-91.

(29.) Boon AJ, Tans JT, Delwel EJ, Egeler-Peerdeman SM, Hanlo PW, Wurzer HA, et al. The Dutch normal-pressure hydrocephalus study. How to select patients for shunting? An analysis of four diagnostic criteria. Surg Neurol 2000;53:201-7.

(30.) Meier U, Bartels P. The importance of the intrathecal infusion test in the diagnostic of normal-pressure hydrocephalus. Eur Neurol 2001;46:178-86.

The Authors

MEG VERREES, M.D., is chief resident in the Department of Neurosurgery at Case Western Reserve University, University Hospitals of Cleveland. She received her medical degree from Dartmouth Medical School, Hanover, N.H.

WARREN R. SELMAN, M.D., is professor and vice chair in the Department of Neurosurgery at Case Western Reserve University, University Hospitals of Cleveland. He received his medical degree from Case Western Reserve University and completed a residency in neurosurgery at Case Western Reserve University, University Hospitals of Cleveland.

Address correspondence to Meg Verrees, M.D., Department of Neurosurgery, Case Western Reserve University, University Hospitals of Cleveland, 11000 Euclid Ave., Cleveland, OH 44106 (e-mail: megverrees@yahoo.com). Reprints are not available from the authors.

The authors indicate that they do not have any conflicts of interest. Sources of funding: none reported.

COPYRIGHT 2004 American Academy of Family PhysiciansCOPYRIGHT 2004 Gale Group

 
© 2006, DrPlace.com, All Rights Reserved.