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Table of Contents    
CORRESPONDENCE
Year : 2019  |  Volume : 67  |  Issue : 3  |  Page : 944-946

Cerebrospinal fluid dynamics study in clinical practice


Department of Neurosurgery, Chettinad Hospital and Research Institute, Kelambakkam, Chennai, Tamil Nadu, India

Date of Web Publication23-Jul-2019

Correspondence Address:
Dr. Vengalathur G Ramesh
Department of Neurosurgery, Chettinad Hospital and Research Institute, Kelambakkam, Chennai - 603 103, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.263213

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How to cite this article:
Ramesh VG. Cerebrospinal fluid dynamics study in clinical practice. Neurol India 2019;67:944-6

How to cite this URL:
Ramesh VG. Cerebrospinal fluid dynamics study in clinical practice. Neurol India [serial online] 2019 [cited 2019 Aug 19];67:944-6. Available from: http://www.neurologyindia.com/text.asp?2019/67/3/944/263213




The study of cerebrospinal fluid (CSF) dynamics is an interesting and under-explored field. There are several conditions in clinical practice which are due to altered CSF dynamics like normal pressure hydrocephalus (NPH), idiopathic intracranial hypertension (IIH), and post-meningitic and post-traumatic hydrocephalus, which often pose challenges in diagnosis and management. In NPH, there is always a diagnostic dilemma, as to whether it is indeed NPH or Alzheimer's/vascular dementia and also whether the patient diagnosed to have NPH will respond well to shunt surgery or not. IIH also may mimic many other conditions. In post-meningitic and post-traumatic hydrocephalus, again, there is always a dilemma as to whether the patient will respond well to a shunt or not. Hence, in these conditions, a CSF dynamics study is of immense use.

There are various methods for the study of CSF dynamics in clinical practice. Some of them are as follows: constant flow infusion method (Katzman method),[1] constant pressure method (Ekstedt's servo-controlled method),[2],[3] bolus lumbar injection method (Marmarou's method [4],[5] and Madras Institute of Neurology (MIN) modification of Marmarou's method [6],[7]) are quantitative methods, while radio-isotope dilution method and phase contrast magnetic resonance imaging (PC-MRI)[8] are more qualitative. Of these, bolus lumbar injection method and the phase contrast (PC)-MRI are used presently in clinical practice. The other methods are mainly used in laboratory research.

The bolus lumbar injection method involves a rapid injection of a small quantity of artificial CSF or saline and studying the response of CSF pressure, and was propounded by Marmarou.[4],[5] The MIN method, which has been devised by the author, is an improvised Marmarou's bolus lumbar injection method, using saline manometer made with easily available bedside material.[6],[7] A saline manometer or an intravenous set mounted on a meter scale is used, which is filled with saline up to 11 cm of water with the zero level corresponding to the level of the spine. Lumbar puncture is performed with a 20G spinal needle connected to the saline manometer through a three-way adapter. The opening pressure (Po) is noted. About 5 or 10 mL (rV) is injected through the three-way port into the subarachnoid space. Peak pressure (Pp) is noted. After an interval of 5 or 10 minutes (t), the pressure reading (Pt) is noted. The CSF outflow resistance (Rout) is calculated using two-step formula described by Marmarou:

I step: Pressure Volume Index (PVI) = rV/log (Pp/Po)

II step: Rout = t.Po/PVI [log Pt (Pp−Po)/Pp (Pt−Po)] cm of water/mL/min.

This is converted into mm Hg/mL/min (cm of water/mL/min divided by 1.36).

The MIN method of CSF outflow resistance measurement is a simple, bedside examination tool and can be performed in a few minutes without any costly sophisticated equipment. The author has used this method for evaluating NPH, post-meningitic and post-traumatic hydrocephalus, and IIH.[9],[10] Rout values of 18 mm Hg/mL/min and above is diagnostic of NPH and predict a good outcome after shunt surgery. High Rout values also were predictive of a good outcome after the shunt placement in post-meningitic and post-traumatic hydrocephalus. In IIH, many a times, the opening CSF pressure (Po) is normal, adding to the diagnostic dilemma. In such situations, Rout measurement helps in the diagnosis of IIH.

In PC-MRI, the signal contrast between flowing and stationary nuclei is generated by sensitization of the phase of the transverse magnetization to the velocity of motion. The anticipated maximum CSF velocity is entered into the pulse sequence protocol. This is also called velocity encoding (VENC). The VENC value selected should be equal or slightly above the anticipated CSF flow velocity so that optimal signal may be obtained. The mean VENC value is 5-8 cm/s for standard CSF flow imaging. In NPH, higher VENC values (20-25 cm/s) are required due to the hyperdynamic CSF flow across the aqueduct. It is possible to obtain both quantitative CSF velocity and qualitative flow information, and it takes only 8–10 minutes more after the routine MRI. Caudal and rostral peak aqueduct CSF flow with a velocity of more than 18 mL/min with pulsatility is characteristic of NPH. PC-MRI is also useful in the evaluation of syringomyelic cysts, Chiari I malformation, evaluation of patency of third ventriculostomy, and evaluation of shunt function. In the article “Change in Average Peak Cerebrospinal Fluid Flow Velocity at Cerebral Aqueduct, before and after Tapping, by Use of Phase Contrast MRI and Its Effect on Gait Improvement in Patients with Normal Pressure Hydrocephalus,” the authors have shown a good correlation between the reduction in CSF peak velocity and the gait improvement following the conduction of lumbar tap test. This adds one more application for PC-MRI in the diagnosis of NPH. With the widespread availability in future, PC-MRI may find more applications in the diagnosis and management of disorders of CSF.[11],[12]

The study of CSF dynamics is finding more applications in clinical practice. Rout measurement using the bolus lumbar injection method and CSF flow velocity, and characterization of CSF flow using PC-MRI are important diagnostic tools in the evaluation of clinical disorders affecting CSF dynamics.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Katzman R, Hussey F. A simple constant-infusion manometric test for measurement of CSF absorption. I. Rationale and method. Neurology 1970;20:534-44.  Back to cited text no. 1
    
2.
Ekstedt J. CSF hydrodynamic studies in man. 1. Method of constant pressure CSF infusion. J Neurol Neurosurg Psychiatry 1977;40:105-19.  Back to cited text no. 2
    
3.
Ekstedt J. CSF hydrodynamic studies in man. 2. Normal hydrodynamic variables related to CSF pressure and flow. J Neurol Neurosurg Psychiatry 1978;41:345-53.  Back to cited text no. 3
    
4.
Marmarou A, Shulman K, LaMorgese J. Compartmental analysis of compliance and outflow resistance of the cerebrospinal fluid system. J Neurosurg 1975;43:523-34.  Back to cited text no. 4
    
5.
Marmarou A, Shulman K, Rosende RM. A nonlinear analysis of cerebrospinal fluid system and intracranial pressure dynamics. J Neurosurg 1978;48:332-44.  Back to cited text no. 5
    
6.
Ramesh VG, Vijay S, Pari K, Mohan Sampathkumar M. CSF dynamics study in clinical practice: An evaluation of the bolus lumbar injection method. Pan Arab J Neurosurg 2005;9:33-6.  Back to cited text no. 6
    
7.
Ramesh VG. Cerebrospinal fluid dynamics study: Applications in clinical practice. Chettinad Health City Med J 2013;2:40-3.  Back to cited text no. 7
    
8.
Battal B, Kocaoglu M, Bulakbasi N, Husmen G, Tuba Sanal H, Tayfun C. Cerebrospinal fluid flow imaging by using phase-contrast MR technique. Br J Radiol 2011;84:758-65.  Back to cited text no. 8
    
9.
Ramesh VG, Vidhya N, Chandramouli B. Cerebrospinal fluid dynamics study in communicating hydrocephalus. Asian J Neurosurg 2017;12:153-8.  Back to cited text no. 9
[PUBMED]  [Full text]  
10.
Ramesh VG. Diagnosis and prediction of surgical outcome in normal pressure hydrocephalus. J Neurosurg 2016;125:783-4.  Back to cited text no. 10
    
11.
Chatterjee S, Harischandra L. Cerebrospinal fluid shunts – How they work: The basics. Neurol India 2018;66:24-35.  Back to cited text no. 11
[PUBMED]  [Full text]  
12.
Gokul UR, Ramakrishnan KG. Change in average peak cerebrospinal fluid velocity at the cerebral aqueduct, before and after lumbar CSF tapping by the use of phase contrast MRI, and its effect on gait improvement in patients with normal pressure hydrocephalus. Neurol India 2018;66:1407-12.  Back to cited text no. 12
[PUBMED]  [Full text]  




 

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