Normal Pressure Hydrocephalus: A Simple Hypothesis

Gardar Gudmundsson

Uppsalir Medical Center, Reykjavik, Iceland.

DOI: 10.4236/ojmn.2013.31002                

Abstract

Normal pressure hydrocephalus is a devious phenomenon. It is a disease that is difficult to diagnose and difficult to treat, the only treatment being a ventriculo-peritoneal shunt, though good shunting results rarely pass a 70% level of effectiveness. We need to understand its pathophysiology better before things will improve. Although some colleagues know it as a possible “reversible dementia” others hardly know about its existence. Solutions would also have value for the general understanding of hydrocephalus of other types. Many theories have been published recently in the search for the missing pieces in this puzzle and I feel that my own postulations could turn out to be useful. After years of diagnosing and operating on hydrocephalus patients I propose that: 1) There is reason to believe that patients with the Apoprotein E3/3 genotype and a high head size percentile are particularly vulnerable to developing idiopathic normal pressure hydrocephalus (iNPH). 2) The classical theory that the arachnoid granulations (AG) transport cerebrospinal fluid (CSF) into the venous circulation is wrong. I postulate, that the AG essentially are sensors, registering the pressure differences between the CSF in the subarachnoidal space at the top of the skull and the venous pressure in the sagittal sinus. The AG’s endothelium produces nitric oxide (NO) as a messenger that is received by the vagus nerve at the jugular foramen. 3) The disease has its fundamental pathology in the subpial space in the large cisternas and along the large vessels under the brain. Here the intravenous absorption of cerebrospinal fluid (CSF) takes place. Cerebrospinal fluid is transported into the subpial venules and veins, driven by the pulse pressure of the subpial arteries. Morphological changes in the pial/subpial anatomy explain the existence of acquired normal pressure hydrocephalus (aNPH).

Keywords

Normal Pressure Hydrocephalus; ApoE3; Head Size; Arachnoid Granulations; Subpial Absorption

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	R. D. Adam, C. M. Fisher, S. Hakim, et al., “Symptomatic Occult Hydrocephalus with ‘Normal’ Cerebrospinal Fluid Pressure. A Treatable Syndrome,” The New England Journal of Medicine, Vol. 273, 1965, pp. 117-126. doi:10.1056/NEJM196507152730301
[2]	N. Relkin, A. Marmarou, P. Klinge, M. Bergsneider and P. M. Blach, “Diagnosing Idiopathic Normal-Pressure Hydrocephalus,” Neurosurgery, Vol. 57, 3 Suppl., 2005, pp. 4-16, Discussions ii-v.
[3]	H. O. Conn and F. M. Lobo, “What Do Physicians Know about Normal Pressure Hydrocephalus and When Did They Know It? A Survey of 284 Physicians,” Yale Journal of Biology and Medicine, Vol. 81, No. 1, 2008, pp. 19-29.
[4]	G. Gudmundsson, G. Kristjansdottir, E. Cook and I. Olafsson, “Association of ApoE Genotype with Clinical Fea tures and Outcome in Idiopathic Normal Pressure Hydrocephalus (iNPH): A Preliminary Report,” Acta Neurochirurgica, Vol. 151, No. 11, 2009, pp. 1511-1512. doi:10.1007/s00701-009-0429-8
[5]	R. K. Wilson and M. A. Williams, “Evidence That Congenital Hydrocephalus Is a Precursor to Idiopathic Normal Pressure Hydrocephalus in Only a Subset of Patients,” Journal of Neurology, Neurosurgery & Psychiatry, Vol. 78, No. 5, 2007, pp. 508-511. doi:10.1136/jnnp.2006.108761
[6]	W. G. Bradley, F. G. Safar, C. Hurtado, J. Ord and J. F. Alksne, “Increased Intracranial Volume: A Clue to the Etiology of Idiopathic Normal-Pressure Hydrocephalus?” American Journal of Neuroradiology, Vol. 25, No. 9, 2004, pp. 1479-1484.
[7]	R. O. Weller, E. Dujanda, H.-Y. Yow and R. O. Carare, “Lymphatic Drainage of the Brain and the Pathophysiology of Neurological Disease,” Acta Neurochirurgica, Vol. 117, No. 1, 2009, pp. 1-14. doi:10.1007/s00401-008-0457-0
[8]	M. Bulat, V. Lupret, D. Oreskovic and M. Klarica, “Transventricular and Transpial Absorption of Cerebrospinal Fluid into Cerebral Microvessels,” Collegium Antropologicum, Vol. 32, Suppl. 1, 2008, pp. 43-50.
[9]	L. Sakka, G. Coll and J. Chazal, “Review of the Literature. Anatomy and Physiology of Cerebrospinal Fluid,” European Annals of Otorhinolaryngology, Head and Neck Diseases, Vol. 128, No. 6, 2011, pp. 309-316.
[10]	J. J. Iliff, M. Wang, Y. Liao, B. A. Plogg, W. Peng, G. A. Gundersen, H. Benveniste, G. E. Vates, R. Deane, S. A. Goldman, E. A. Nagelhus and M. Nedergaard, “A Paravascular Pathway Facilitates CSF Flow through the Brain Parenchyma and the Clearance of Interstitial Solutes, Including Amyloid β,” Science Translational Medicine, Vol. 4, No. 147, 2012, Article ID: 147ra111.
[11]	M. Egnor, A. Rosiello and L. Zheng, “A Model of Intracranial Pulsations,” Pediatric Neurosurgery, Vol. 35, No. 6, 2001, pp. 284-298. doi:10.1159/000050440
[12]	K. Hirata, T. Yaginuma, M. F. O′Rourke and M. Kawakami, “Age-Related Changes in Carotid Artery Flow and Pressure Pulses: Possible Implications for Cerebral Microvascular Disease,” Stroke, Vol. 37, No. 10, 2006, pp. 2552-2556. doi:10.1161/01.STR.0000242289.20381.f4
[13]	T. Greenhalgh, “How to Read a Paper,” 4th Edition, BMJ Books, London, 2010, pp. 166-167.