Lumbar infusion test for the investigation of normal pressure hydrocephalus (interventional procedures consultation)
NATIONAL INSTITUTE FOR HEALTH AND CLINICAL EXCELLENCE
Interventional Procedure Consultation Document
Lumbar infusion test for the investigation of normal pressure hydrocephalus
| Normal pressure hydrocephalus (NPH) is a condition in which a clear, colourless fluid called cerebrospinal fluid (or CSF) accumulates around the brain and spinal cord. Symptoms include problems with walking, bladder control, memory and thinking clearly. Some patients respond well to surgical treatment (called 'shunt surgery'). The lumbar infusion test may be useful for selecting patients who are likely to benefit from this type of surgery. This test involves the insertion of a needle through the skin of the lower back into the spine. Measurements are then taken of the CSF pressure as fluid is injected into the spine. |
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The National Institute for Health and Clinical Excellence is examining the lumbar infusion test for the investigation of normal pressure hydrocephalus and will publish guidance on its safety and efficacy to the NHS in England, Wales, Scotland and Northern Ireland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisers, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about the lumbar infusion test for the investigation of normal pressure hydrocephalus.
Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation. The process that the Institute will follow after the consultation period ends is as follows.
For further details, see the Interventional Procedures Programme manual, which is available from the Institute's website (www.nice.org.uk/ipprocessmanual). NICE is committed to promoting through its guidance race and disability equality and equality between men and women, and to eliminating all forms of discrimination. One of the ways we do this is by trying to involve as wide a range of people and interest groups as possible in the development of our guidance on interventional procedures. In particular, we aim to encourage people and organisations from groups in the population who might not normally comment on our guidance to do so. We also ask consultees to highlight any ways in which draft guidance fails to promote equality or tackle discrimination and how it might be improved. Closing date for comments: 27 March 2008 |
| Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation. |
| 1 | Provisional recommendations |
| 1.1 | Current evidence on use of the lumbar infusion test for the investigation of normal pressure hydrocephalus (NPH) raises no major safety concerns. In terms of efficacy, some clinicians find the procedure helpful in the investigation of NPH. Therefore, it may be used with normal arrangements for clinical governance, consent and audit. |
| 2 | The procedure | ||
| 2.1 | Indications and current treatments | ||
| 2.1.1 | NPH is an accumulation of cerebrospinal fluid (CSF) around the brain and spinal cord, which can cause symptoms such as abnormal gait, urinary incontinence and impaired cognitive function. It usually occurs in the elderly, and is characterised by enlarged cerebral ventricles but with normal CSF pressure on lumbar puncture. | ||
| 2.1.2 | Conventionally, NPH is treated surgically, by inserting a shunt which diverts CSF from the brain (or lumbar spinal sac) to the abdominal cavity where it is then absorbed into the circulation. This may relieve gait disturbance, help prevent permanent loss of cognitive function and halt the progression of other symptoms. | ||
| 2.1.3 | It is important to diagnose NPH correctly as shunting may be unnecessary (and also potentially harmful) when symptoms are caused by conditions other than NPH, such as degenerative cerebral atrophy. Diagnosis of NPH based on clinical and radiological signs alone can be problematic so additional testing may be required. Conventionally, this includes a large volume lumbar puncture test (also known as a spinal or CSF tap test). A baseline clinical evaluation is performed, typically including a mini-mental state examination and walking tests. Under local anaesthetic, a spinal needle is inserted between the lumbar vertebrae into the spinal sac and CSF is collected. Several hours later the clinical evaluation is repeated to assess the effect of removing CSF. Clinical improvement after the lumbar puncture (which may be sustained for several days or weeks) indicates that the patient may benefit from shunting; however, the test is not completely reliable. | ||
| 2.2 | Outline of the procedure | ||
| 2.2.1 | The lumbar infusion test (also known as the intrathecal infusion test) aims to assess the adequacy of CSF absorptive capacity by the administration of a fluid challenge. An abnormal and sustained rise in CSF pressure in the face of the challenge is indicative of reduced absorptive capacity and, therefore, of NPH. | ||
| 2.2.2 | Under local anaesthetic, a needle connected to a pressure monitor is inserted through the skin of the lower back and into the lumbar spinal sac. CSF pressure is then recorded and monitored as fluid is infused. A common measure used to determine which patients are most likely to benefit from shunt surgery is the resistance to CSF outflow (measured in mmHg/ml/min), which is calculated from the pressure gradient (mmHg) during a constant infusion (ml/min). Alternatively, the plateau pressure (measured in mmHg), at which a balance between CSF absorption and infusion is reached, may be used. Various numerical cut-off points in the test have been used to assess the likelihood that a given patient may benefit from subsequent shunt surgery. | ||
| Sections 2.3 and 2.4 describe efficacy and safety outcomes which were available in the published literature and which the Committee considered as part of the evidence about this procedure. For more details, refer to the sources of evidence (see appendix). | |||
| 2.3 | Efficacy | ||
| 2.3.1 | A case series of 101 patients, which assessed the ability of CSF outflow resistance (measured by the lumbar infusion test) to predict the response to shunting, reported that 92% (33/36) of patients with a CSF outflow resistance greater than 18 mmHg/ml/min (n = 36) had improved scores after shunting (measured on a neurological outcome scale incorporating measures of gait and dementia). However, two thirds of patients with CSF outflow resistance below 18 mmHg/ml/min (n = 59) also showed some clinical improvement (absolute numbers not given). | ||
| 2.3.2 | In a case series of 83 patients, 80% (66/83) met the criteria for shunt surgery, using a threshold of greater than or equal to 12 mmHg/ml/min for CSF outflow resistance or highly suggestive symptoms. Clinical improvement (based on a consensus between the neurologist and the patient) was reported in 59% (39/66) of these patients at minimum follow-up of 1 year. | ||
| 2.3.3 | In a second case series of 83 patients, only 30 underwent lumbar infusion testing, of whom 63% (19/30) met the criteria for shunt surgery, using a threshold of greater than or equal to 16 mmHg/ml/min for CSF outflow resistance). Of those who underwent shunt surgery, 90% (17/19) improved clinically after surgery. Of the patients who did not undergo shunt surgery, 73% (8/11) had no clinical change at median follow-up of 8 months (the final three patients were lost to follow-up). | ||
| 2.3.4 | In a case series of 68 patients who underwent both a lumbar infusion test and a CSF tap test, 68% (47/68) met the criteria for, and underwent, shunt surgery. Of the 38 patients who improved after surgery, 84% (32/38) had a positive lumbar infusion test and 42% (16/38) had a positive CSF tap test (using a threshold value of greater than or equal to 22 mmHg for plateau pressure). Of the nine patients who did not improve clinically, one had a negative lumbar infusion test and eight had a negative CSF tap test. | ||
| 2.3.5 | A case series of 200 patients who underwent shunt surgery reported on 155 patients who were followed up for 7 months. Patients with a CSF outflow resistance greater than 15 mmHg/ml/min had significantly more favourable clinical outcomes than patients with a lower CSF outflow resistance (p = 0.01). | ||
| 2.3.6 | The Specialist Advisers considered key efficacy outcomes to include diagnosis of NPH and clinical or functional outcomes of CSF diversionary procedures. | ||
| 2.4 | Safety | ||
| 2.4.1 | Five of the six reports described no adverse events related to the lumbar infusion test. In the case series of 200 patients who underwent the lumbar infusion test, 19% of the 107 patients with a positive test result reported headache after the test (absolute number not reported) and 2% (2/107) were reported to have developed meningism without signs of CSF inflammation. | ||
| 2.4.2 | The Specialist Advisers considered theoretical adverse events to include infection, post-procedure headache, bleeding, localised pain and nerve root damage. | ||
Bruce Campbell
Chairman, Interventional Procedures Advisory Committee
February 2008
| Appendix: | Sources of evidence |
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The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.
Available from: http://www.nice.org.uk/guidance/index.jsp?action=download&o=39662. |
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This page was last updated: 30 March 2010