THE FULL RATIONALE AND DRAFT PROTOCOL ARE ATTACHED. HERE IS A SKELETON
SUMMARY:
(For those of you who aren't familiar with this physical sign: during
fundoscopy, if you look at the retinal veins just before they disappear
into the optic disk, you will see them pulsate (either laterally, so that
they get fatter and skinnier with each cardiac cycle, and/or sometimes in
the form of an alternating longitudinal movement of the light reflex
along the vein's surface). It's quite a revelation the first time you see
it, especially if you've been examining eyes for a long time and never
noticed it before!)
I've used it for years as an index of intracranial pressure, but the
evidence on its usefulness for this purpose is scant. Accordingly, here
is a first "go" at a proposal for a CARE study investigating spontaneous
retinal vein pulsation (SRVP) as a means of ruling-out clinically
important elevated intracranial pressure (high-ICP).
I'm sending it out to all current and prospective CARE members with two
requests:
1. That any of you who are interested please respond to me with
suggestions for improving this draft protocol.
2. that all of you forward it (with encouragement!) to any non-CARE
colleagues whom you think might be interested in contributing to its
design and execution (I'm thinking of emergency/A&E/trauma clinicians,
Infectious Disease clinicians, General Internists, Neurologists,
Neurosurgeons, Oncologists, and Paediatricians, but there are undoubtedly
more who might be interested).
Proposed Primary Clinical Question:
In patients with clinically suspected high intracranial pressure
(high-ICP) and intact crania, does the presence of spontaneous retinal
vein pulsation (SRVP) rule-out clinically important high-ICP?
Proposed Secondary Clinical Questions:
If you see SRVP, can a lumbar puncture (LP) be done without causing brain
herniation through the foramen magnum?
Can you safely omit CT headscans for ruling-out high-ICP prior to lumbar
puncture if you see SRVP?
Justification from studies of normal individuals:
First, Walsh et al confirmed SRVP in a convenience sample of 9 Neurology
patients and then watched their SRVP as they underwent lumbar puncture and
the Queckenstedt manoeuvre (in which compressing the jugular veins raises
ICP and, if all is normal, "communicates" this rise to the spinal fluid
and raises the CSF level in a manometer attached to the LP needle). He
documented that:
SRVP disappeared when spinal fluid pressure rose past 204 (+/- 17) mm H2O
SRVP reappeared when spinal fluid pressure fell past 201 (+/- 17) mm H2O
[Walsh TJ, Garden JW, Gallagher B: Obliteration of retinal venous
pulsations during elevation of cerebrospinal-fluid pressure. Amer J
Ophthalmology 1969;67:954-6.]
Second, Lorentzen documented that SRVP was present in one or both eyes in
91% of females and 88% of males ages 10-79 (no decline with advancing
age!). SRVP was slightly more likely to be present in the right (87%) than
left (75%) eye.
(Lorentzen: Acta Ophthalmologica 1970;48:765-770)
Justification from studies of patients with clinically-suspected increased
ICP:
Levin examined SRVP in 43 patients he was convinced really had high ICP
(by lumbar puncture >190 mm H20 [oops!], findings at surgery, or
convincing clinical evidence of brain herniation) and in 189 patients he
was convinced really had normal ICP (by the absence of any signs,
symptoms, or suspicion that they might have high ICP). No patient with
high ICP had SRVP. That is, if we think of the loss of SRVP as the
abnormal sign, it had a sensitivity of 100% for high ICP in this small
study, and the presence of SRVP "SnNouts" clinically important high-ICP.
88% of the 189 "normal" patients had SRVP (specificity = 88%), so the
absence of SRVP is only suggestive, but not diagnostic, of high-ICP (it
doesn't "SpPin" this diagnosis). [Levin BE: The clinical significance of
spontaneous pulsations of the retinal vein. Arch Neurol 1978;35:37-40]
I have asked every neurologist/neurosurgeon I know about this sign. All
but one knew about it, most used it, and only one reported ever seeing
SRVP in a patient with high-ICP, but he was a dean (I mean the doctor, not
the patient!).
Safety:
The anecdotal experience (that needs refutation or validation!) on our
clinical service is that uncooperative patients and non-expert examiners
result in under-reading rather than over-reading SRVP (that is, they
report SRVP to be absent when, in fact, it is present). Since patients
would bypass CT scanning only when SRVP was present, the errors fall on
the side of clinical safety (albeit inefficiency).
The first "go" at a protocol is attached.
Please join it and make it better.
thanks and cheers,
dls
............................................................................
Prof David L. Sackett
Director, NHS R&D Centre for Evidence-Based Medicine
Consultant in Medicine Editor, Evidence-Based Medicine
Nuffield Department of Medicine, University of Oxford
Level 5, John Radcliffe Hospital, Oxford OX3 9DU, England
Phone: +44-(0)1865-221320 Fax: +44-(0)1865 222901
Email: [log in to unmask] WWW: http://cebm.jr2.ox.ac.uk
As of 1 June 1999: The Kilgore Trout Research, Chainsaw Management,
and Conference Centre at Irish Lake,
RR #1, Markdale, Ontario, Canada N0C 1H0
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