Is it a stroke?
BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h56 (Published 15 January 2015) Cite this as: BMJ 2015;350:h56
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This is an excellent review but unfortunately cerebral gas embolism (CGE) has not been mentioned as a cause of stroke.
CGE is an iatrogenic complication of numerous medical procedures, including peripheral intravenous lines, and in patients with a peri-procedural stroke the diagnosis of CGE should always be entertained. The management is different and often very effective, namely hyperbaric oxygen therapy, in addition to supportive therapy. Although urgent treatment, i.e. within 6 hours is ideal, there are many reports of excellent response to hyperbaric treatment given up to 48 hours later 1 2.
There may be preceding haemodynamic disturbances which could alert clinicians to the possibility but very often the presenting signs are like strokes in general with a large variety of neurological signs and symptoms as presentation. Nobody really knows what the real incidence is and a high index of suspicion is important 3. Occasionally the circumstances are very clear and time should not be wasted with imaging, however in many instances a CT could be arranged very quickly without much delay in arranging transfer to an appropriate centre where full intensive care support can be given in the hyperbaric chamber. It is important to be aware that imaging is not very sensitive and in some cases bubbles can disappear very quickly but the damage continues 2.
The last point we would like to highlight is the concept of retrograde cerebral venous gas embolism. This may have a slower onset and may have more benign outcome, however it is important to realise that without appropriate management it is also fatal in many instances 4 5.
References:
1. Bessereau J, Genotelle N, Chabbaut C, et al. Long-term outcome of iatrogenic gas embolism. Intensive Care Medicine 2010;36(7):1180-87
2. Moon RE. Hyperbaric oxygen treatment for air or gas embolism. Undersea & hyperbaric medicine: journal of the Undersea and Hyperbaric Medical Society, Inc 2014;41(2):159-66
3. Bothma PA, Schlimp CJ. II. Retrograde cerebral venous gas embolism: are we missing too many cases? Br J Anaesth 2014;112(3):401-4
4. Schlimp CJ, Loimer T, Rieger M, et al. The potential of venous air embolism ascending retrograde to the brain. Journal of forensic sciences 2005;50(4):906-9
5. Fracasso T, Karger B, Schmidt PF, et al. Retrograde Venous Cerebral Air Embolism from Disconnected Central Venous Catheter: An Experimental Model. Journal of Forensic Science 2011;56(S1):S101-S04
Competing interests: No competing interests
I read with great interest the excellent article by Professor Graeme J Hankey and David Blacker (1) on the practical approach to the diagnosis and management of stroke. One of the important problems, is the weakness of the FAST Tool to detect posterior fossa strokes in some patients that might not alert triaging to these patients to stroke physicians and neurologists in the hyperacute centres.
Over the past three years I have not been involved in the management of hyperacute strokes, but sporadically I have met patients who have been effectively screened by the paramedics with the FAST tool that has not unravelled symptoms arising from the posterior fossa. Both FAST and ABCD2 scores were less effective in the diagnosis, and identification, of high risk cases for posterior circulation stroke and TIA (2). The same team have suggested including additional parameters in these screening tools, particularly the presence or absence of visual disturbance, can improve the sensitivity with the challenge that it might not keep a good specificity. In a small retrospective assessment, we also showed that inclusion of ataxia and/ or visual disturbances would have improved the earlier detection and triaging posterior fossa strokes for which we proposed FAST –AV or AB (3). The time is due for Stroke Association to sponsor a study to improve on the FAST Tool to cover strokes and TIAs of the posterior Fossa particularly major basilar artery stroke.
References
1. GJ Hankey, DJ Blacker. Is it a stroke? BMJ 2015;350:h56
2. G.Gulli and HS Markus. The use of FAST and ABCD2 scores in posterior circulation, compared with anterior circulation, stroke and transient ischemic attack J Neurol Neurosurg Psychiatry. doi:10.1136/jnnp.2010.222091
3. F. Huwez, E. Casswell. FAST-AV or FAST-AB tool improves the sensitivity of FAST screening for detection of posterior circulation strokes. International Journal of Stroke 2013; 8: E3, letter.
Competing interests: No competing interests
Re: Is it a stroke?
We thank Dr Huwez for highlighting the deficiencies of the Face Arm and Speech Test (FAST), which records the presence of acute facial paresis, arm drift or abnormal speech, in diagnosing posterior circulation strokes.
The FAST is a useful screening tool in the community because most strokes involve the anterior circulation and therefore affect at least one of the three components measured by the FAST. However, for the important minority of posterior circulation strokes (and some anterior circulations strokes), function of the face, arm and speech may not be affected and hence the FAST may not alert the observer to the diagnosis of stroke.
We welcome efforts by Dr Huwez and colleagues to examine the predictive value of common symptoms of posterior circulation stroke (e.g. vertigo, ataxia, diplopia, hemianopia) for stroke and to develop and validate a formula that optimises the sensitivity of the FAST for diagnosing all strokes in the community without compromising specificity unacceptably.
Competing interests: No competing interests