DETECTING INTRACRANIAL PRESSURE WAVES WITH ULTRASOUND

355 METHOD

Patients were given pethidine (75 mg.) and promethazine (25 mg.) one hour before and 5 mg. of intravenous diazepam at the start of the procedure. A large-bore Tuohy needle was inserted into the theca, usually through the L5-sl

interspace. c.s.F. was withdrawn in 10 ml. amounts into syringe and replaced. This sequence was repeated 15-20 times, and it was commonly found that after about

a

replacements patients remarked that their pain had been relieved. Initially, technical difficulty was encountered from obstruction of the end of the needle by contact with nerve-roots, which often caused momentary pain down the leg. This problem was overcome by the use of the Tuohy needle which has a large bore and a lateral aperture.

ten

RESULTS

DISCUSSION

parts of the

spinal cord. We are now measuring changes during c.s.F. barbotage. by

a

grant from the

Spastics Society

Requests for reprints should be addressed to J. W. L., Abingdon Pain Relief Unit, Abingdon Hospital, Marcham Road, Abingdon, Berkshire. REFERENCES 1.

2. 3. 4. 5.

Department of Neurosurgery, St. George’s Hospital, Atkinson Morley’s Hospital, London S.W.20

at

Twenty-two patients who were undergoing continuous monitoring of intracranial pressure (I.C.P.) were subjected to one or more ultrasound recordings lasting 1-3 hours. The change in magnitude of the midline echo was compared with the wave-forms of the I.C.P. trace. In twelve patients Summary

and distinctive patterns occurred

simultaneously in the ultrasound tracing. These patterns were easy to reproduce and were never seen in the absence of I.C.P. waves. There was no difference in ultrasound tracings at normal I.C.P. compared with tracings at raised pressure in the absence of pressure waves.

Relief of severe, intractable pain is a problem in the management of certain diseases, especially in the terminal care of some cases of malignant tumour. Various methods of relieving pain are available, but most have disadvantages or limitations. The use of analgesics is limited by the side-effects encountered when they are used in the high dosages required to abolish severe pain. The intrathecal injection of toxic agents such as phenol and alcohol may cause paralysis of the bladder or bowel. The introduction of ice-cold saline solution into the theca is so painful that a general anxsthetic is usually required. The technique of C.S.F. barbotage is a valuable addition to other methods of pain relief. It is usually successful, and sometimes has been dramatically effective. If the pain recurs the procedure can be repeated as many times as necessary. The technique is simple and requires no complex apparatus. No adverse effects of any kind occurred in our patients treated by this method. The mechanism by which barbotage relieves pain is not clear. Preliminary necropsy examinations showed slight peripheral degeneration of the spinal cord which resembled that produced by Bunge et al.3-5 in cats, but was much less widespread and intense. Involvement of spinothalamic fibres traversing this region of the spinal cord may explain the beneficial effect. The way in which barbotage damages this peripheral zone is unknown, but Bunge et al. suggested that a local pressure effect was exerted on certain

This work was supported for technical assistance.

I. D. EVERSDEN ALAN RICHARDSON W. C. A. STERNBERGH, JR.

I.C.P. waves were seen

The results are summarised in the accompanying table. Of 14 patients, 4 had no relief from pain. The remaining 10 had periods of pain relief varying from two days to three months.

pressure

DETECTING INTRACRANIAL PRESSURE WAVES WITH ULTRASOUND

Gillman, T., Gillman, J. Am. J. med. Sci. 1946, 211, 448. Barth, E. Z. ges. inn. Med. 1958, 13, 1003. Bunge, R. P., Settlage, P. H. J. Neuropath. exp. Neurol. 1957, 16, 471. Bunge, R. P., Bunge, M. B., Ris, H. J. biophys. biochem. Cytol. 1960, 7, 685. Bunge, M. B., Bunge, R. P., Ris, H, ibid. 1961, 10, 67.

INTRODUCTION

MINIATURE pressure transducers now permit intracranial pressure (I.C.P.) to be measured reliably and continuously.1,2This is especially useful in cases of head injury or intracranial space-occupying lesions. However, minor operations are required to install and remove the transducer, and there is a small risk of wound infection. Echoencephalography is a safe, reliable, and nonsurgical technique for displaying the midline of the intracranial structures, and several investigators have reported a relationship between l.c.p. and the pulsation In 1964 jeppssonreported of the midline echo. variations in the amplitude of ultrasound echoes which strongly resembled the arterial pressure wave-form. He found that the time taken for an echo to pulsate from its minimum to maximum height (rise-time) was significantly shorter for those patients with raised l.c.p.— a finding which was later confirmed by ter Braak and de Vlieger.4 However, Campbell et al.,5 in a comprehensive and careful study, reported a range of rise-time for normal subjects which overlapped normal and pathological values previously reported. Investigations at this firm also failed to criteria for abnormal hospital identify rise-times. However, longer-term changes were noticed in echo amplitude which did correlate with changes in l.c.p. These observations form the basis of this report. METHOD

Ultrasound equipment used for echoencephalographic studies in the ward was modified to provide a record of echo pulsation. A gate added to the amplifier circuit of a Smith’s mark 7 ultrasonic flaw detector (Nuclear Enterprises N.E. 4120A ’Diasonoscope ’) allowed any section of the echo display to be isolated from the remainder of the signal. The position of the gate is identified as a brightened portion of the echo display. The midline structures may not be represented as a single echo, so the amplitude of the highest echo within this gate is measured by a peak detector and displayed using a galvanometer pen-recorder. The signal is filtered to eliminate the 50 Hz repetition frequency of the ultrasound generator.

356

A. pulse amplitude B. echo

magnitude

Fig. 1-Terminology used for ultrasound recording.

All recordings

were

made with 30

diameter, 1 MHz cylindrical probes only 14 mm. deep. A head bandage is all that is required to hold this type of probe firmly in place. Stable recordings of the echo pulmm.

sation lasting several hours can be Fig. 3-Simultaneous recording of echo pulsation and I.C.P. during B waves. obtained. and identical frequency to the i.c.p. waves are observed Simultaneous recordings of I.c.p. were made using intrain the ultrasound tracing, and there is a change of durally implanted miniature pressure transducers modified to allow in-situ calibration.2 pulse amplitude as the I.C.P. rises and falls. Because a

specific Twenty-two patients had extended ultrasound recordings while undergoing continuous monitoring of Each recording lasted at least 1 hour, and l.c.p. frequently 3-5 recordings were obtained over several days. Diagnoses of patients were intracranial tumour (thirteen), head injury (five), and hydrocephalus (four). Recordings were made at the bedside without interrupting intensive nursing care. Many patients were critically ill, and bulky devices for immobilisation of the head and ultrasound probe could not be used. With experience and patience many hours of suitable tracings were obtained. Normal ultrasound recordings show waves which closely resemble the arterial pulsation and slower waves which correspond to respiration: these wave-formsare identified in fig. 1 as " pulse amplitude ". Longer-term changes in the height of the echo are called " echo magnitude " (fig. 1). Twelve patients had intermittent i.c.p. waves. The ultrasound tracings during these waves show distinct changes. A plateau wave is a rapid rise in I.C.P. which may exceed 100 mm. Hg.This increase is maintained for 5-45 minutes, then abruptly falls to the basal level. During the increase of pressure the echo magnitude decreases so sharply that the gain of the echo display often has to be increased. The rise in pulse pressure which accompanies a rise of l.c.p. is reflected as an increase of pulse amplitude of the ultrasound trace. These changes are maintained during the period of increased pressure, reverting to the normal appearance as the plateau wave subsides (fig. 2). Other i.c.p. waves (" B waves) occur repetitively "

about

once

a

minute with

a

pressure increase of

Hg. These are thought to be an earlier stage of vascular decompensation than plateau waves. During B waves distinct patterns are seen in the ultrasound recording (fig. 3). Waves of similar magnitude 10-40

mm.

echo may

move

either up

or

down with

systole, the ultrasound pattern may be either direct or mirror image facsimile of the intracranial

cardiac

RESULTS

a

In the absence of i.c.p. waves the ultrasound may show random fluctuations in echo magnitude. These are not to be confused with ultrasound waves occurring during I.C.P. waves, which have a regular pattern. There is no discernible difference between tracings recorded at normal and increased I.C.P. if this increase is not accompanied by pressure wave.

tracing

waves.

DISCUSSION

For these observations to have practical application, the ultrasound patterns must be easily distinguishable from the artefacts within echo recordings. Distortion of the probe/scalp/skull interface, and compromise of the upper airway, have been the principal sources of artefact during extended ultrasound recording. Mechanical artefacts caused by movement of the probe in relation to the skull are easily recognised by a sudden, gross deflection from the previous pattern, as well as by association with obvious patient movement. With the small, flat probe secured to the scalp by an ordinary crepe bandage, adequate lengths of recording for analysis can be obtained from almost all patients. Upper-airway obstruction, the Valsalva manoeuvre, or any mechanism which abruptly changes the venous pressure causes large fluctuations in the ultrasound recording. Again these distortions are easily recognised on the ultrasound recording and correlate well with simple observation of the patient. The wave-forms seen in the ultrasound tracing which correlate with the i.c.P. waves are not subtle changes. The amplitude of the waves is usually large, and the regularity of their appearance is quite unmistakable. Extended ultrasound recordings in forty subjects without known intracranial lesions or in-

357

creased pressure never demonstrated patterns similar to the waves described above. Similarly, prolonged recordings in ten patients with increased l.c.p. to levels

cranial lesions or in patients with increased I.C.P. but without pressure waves. Some patients with i.c.p. waves have been difficult to study because of restless-

Hg without pressure waves revealed patterns. The source of these changes in echo magnitude is uncertain. de Vlieger and Ridder7 suggested that changes in the magnitude of the midline echo are caused by distortion of the third ventricle. Changes in blood volume, such as those described by Risberg et al.,8 during plateau waves could cause sufficient ventricular distortion to produce the observed changes

ness.

of 40-60

mm.

no I.C.P. wave

in echo

magnitude. CONCLUSION

If the recorded

change in height of the midline echo is during l.c.p. waves, distinctive wave patterns are produced. These patterns are easily recognised and correlate well with the I.C.P. waves. The equipment and technique used to obtain these tracings is not elaborate and can be used on critically ill patients without interfering with nursing care. Similar wave patterns have not been seen in the absence of l.c.p. waves in patients without intra-

Reviews of Books Diagnosis and Treatment

of Abdominal Abscesses

by IRVING M. ARIEL, M.D., F.A.c.S., associate clinical professor of surgery; and KIRK K. KAZARIAN, M.D., assistant professor of surgery, New York Medical College. Baltimore: Williams & Wilkins. Edinburgh: Churchill-Livingstone. 1971. Pp. 322.$17.50; E8. Edited

GOOD in parts, but this curate’s egg lacks much of the There is a very useful chapter on gram-negative shock alongside chapters on aetiology, bacteriology, and radiology. It is interesting to learn about combined lungliver scanning in a report of its successful use in 32 cases (only 3 incorrect diagnoses), but not very useful, for, though the author regards the investigation as simple, it would be beyond the compass of most centres. It is odd that a book on abdominal abscess, which includes liver abscess, hydatid cyst, anorectal fistula, and a somewhat anecdotal chapter on the role of urinary infection, fails to give more than passing reference to perinephric, psoas, and appendix abscesses. Psoas abscess has connotations other than tuberculosis of the spine and can occur in association with Crohn’s disease and appendicitis. Surely appendix abscess warrants at least a chapter ? Pelvic abscess is seen from a gynxcological standpoint. To the gynaecologist, pelvic abscess is secondary to a septic tube lying in the area; it comes as no surprise, therefore, that an aggressive approach with early surgery is advocated, in a section in which the difference between a pelvic and a tubo-ovarian abscess becomes progressively ill-defined. The admission that injury to the intestinal tract is a major complication of this regimen raises more than a suspicion that it is, in fact, important to distinguish between tubo-ovarian abscess and pelvic abscess, especially since the injuries are stated to be minor with no statement about fistula. The book suffers from inadequate editorial planning. As a collection of contributions by 24 different authors it is not without value, but two opening chaptersone historical and the other a classical topographical description of the disposition of the peritoneum and how it comes about embryologically-are irrelevant. Pus is where

yolk.

were

With perseverance, however, adequate tracings obtained which always verified the presence of the

I.C.P. waves.

This technique will complement existing methods for continuously monitoring iC.P., since it can select those patients who have I.C.P. waves. These individuals are at risk of sudden clinical deterioration and would benefit from continuous i.c.p. monitoring.1 We thank the Cancer Research Campaign for a grant, our neurosurgical colleagues for permission to study their cases, and Miss J. Beattie for technical assistance. Requests for reprints should be addressed to A. R. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.

Richardson, A., Hide, T. A. H., Eversden, I. D. Lancet, 1970, ii, 687. Eversden, I. D. Med. biol. Engng, 1970, 8, 159. Jeppsson, S. Acta chir. scand. 1964, 128, 218. ter Braak, J. W. A., de Vlieger, M. Acta neurochir. (Wien), 1965, 12, 678. Campbell, J. K., Clark, J. M., White, D. N., Jenkins, C. O. Acta neurol. scand. 1970, 46, suppl. 45. Lundberg, N. Acta psychiat. neurol. scand. 1960, 36, suppl. 149. de Vlieger, M., Ridder, H. J. Neurology, Minneap. 1966, 16, 1033. Risberg, J., Lundberg, N., Ingvar, D. H. J. Neurosurg. 1969, 31, 303.

you find it, and nobody would stop for a moment to recall the topography of the peritoneum before releasing the pus.

Outline of Radiology Louis KREEL, M.D., M.R.c.P., F.F.R., head of radiology, Clinical Research Centre, Northwick Park, and radiologist in administrative charge, Northwick Park Hospital, Harrow. London: William Heinemann Medical Books. 1971. Pp. 377. E6.

Dr. Kreel has provided a comprehensive collection of notes, covering the radiology of all systems of the body in less than 400 pages. An account of the radiological anatomy of each system is followed by a summary of the radiological investigations and techniques used and by the interpretation of the X-ray appearances. The points made in the notes are illustrated by simple line drawings. The precis method of presentation used is useful for pre-examination cramming or for ready reference, and it is to these two purposes that the book is directed. The reader who attempts to read it as a book will require exceptional powers of concentration. Interest cannot be long sustained by such undiluted matter. Within its limits this book is nevertheless a useful teaching contribution, and, since it contains no radiographs, it is cheap as radiological books go. staccato

Biochemistry

of Antimicrobial Action

T. J. FRANKLIN and G. A. SNOW, Imperial Chemical Industries Ltd., Alderley Park, Macclesfield, Cheshire. New York and London: Academic Press. 1971. Pp. 163. $7; S2.25.

BIOLOGY undergraduates, medical students, doctors, and others will find in this book a readable and easily understandable account of the mode of action of the principal The antibiotics, sulphonamides, and related drugs. history of chemotherapy is an exciting one, and, although the opening chapter of this book is too short to capture the fascination of the subject, it is an interesting and useful introduction. The chapter on those antibiotics which affect the bacterial cell wall is likely to be of the most general interest, not simply because of the penicillins but also