Postgrad Med J: first published as 10.1136/pgmj.24.267.11 on 1 January 1948. Downloaded from

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,HE BLOOD SUPPLY OF NERVES By ARCHIBALD DURWARD, F.R.S.(Ed.), M.D., M.B., Ch.B. Professor of Anatomy, University of Leeds. Considerable attention has been given to the one would stress that this does not alter the blood supply of nerves in the past few years. This essential plan, namely, that each nerve receives does not imply that nothing was previously known; along its course a variety of nutrient arteries com- Adams (I942) reviewed the literature on the blood ing from adjacent vessels. It is true that in certain supply of nerves and brought together the widely positions more sizable arteries are occasionally scattered and surprisingly extensive information found associated with nerves, e.g., the sciatic and on that topic. Much of the present-day interest median, and such vessels running on the nerve for naturally derives from the great numbers of peri- considerable distances are to be regarded rather pheral nerve casualties which have arisen in the as embryological persistences and do not imply war. A more detailed conception of the whole that the nerves concerned are receiving any pattern of the vascularization of peripheral preferential vascular supply. nervous tissues is now available and a good deal A detailed and lucid account of the anatomy of of e x p e r i me nt a evidence in this field has the nutrient arteries to the nerves of upper limb accumulated. and to certain nerves of the lower limb has recently There undoubtedly has been some kind of been Sunderland a and that the blood of nerves was of given by (i945, c). assumption supply by copyright. no great moment. Peripheral nerves have been Epineural Vessels treated surgically with a total lack of respect for the arteries or the veins associated with them. On reaching the nerve, these small local nutrient Similar treatment has not been accorded to the gut arteries generally divide into ascending and de- or the central nervous system. That extensive scending branches which course in the epineurium. operations can be, and commonly are, successfully There may be a number of such epineural vessels, carried out on peripheral nerves, with little or no often visible to the naked eye. Sometimes such thought as to their blood supply, strongly suggests vessels pass deeply into the nerve and run between that the pattern of vessels in nerves is peculiar and the fasciculi. From these primary divisions of the is so disposed as to allow extensive mobilization nutrient artery secondary branches are given off http://pmj.bmj.com/ without essential devascularization. The surgeon penetrating more deeply and dividing further. has long acted, maybe unwittingly, on this The vessels concerned are arranged predominantly assumption. This paper will be concerned with in a longitudinal fashion in the perineural or inter- a review of our knowledge regarding the blood fasicular connective tissues. Finally, by repeated supply of nerves and of recent experimental work branchings, the finest vessels penetrate within the in this field. fasciculi and form there a capillary bed, again arranged mainly in a longitudinal fashion with Nutrient Arteries of Nerves numerous cross connections. Vessels of pre- on September 23, 2021 by guest. Protected .capillary size may be found at times within the There are no major arteries specifically devoted actual fasciculi but most the intra- to the supply of nerves. Each nerve, large or generally small, receives nutrient twigs from adjacent fascicular vessels are of the capillary order. arteries. Such nutrient vessels are generally short, and although their size is variable, many of The Intrafascicular Plexus them may be seen with the naked eye. These are This intrafascicular plexus is common to all the local sources of supply presenting as much varia- nutrient arteries and is continuous throughout the tion in actual position as do vessels elsewhere. length of the nerve. It is fed, or reinforced at Some are more or less predictable in position, e.g., various levels, by the nutrient arteries, but no one at the elbow in the case of the ulnar nerve, and in nutrient artery may be considered as dominating the spiral groove in the case of the radial nerve any portion of the plexus. The arrangement out- (Sunderland, I945), but from case to case a good lined above is virtually the antithesis of the ' end deal of variation may be found, and variations on artery ' conception : it is an arrangement whereby the two sides of the body are not uncommon. But a rich continuous capillary bed occupies the length Postgrad Med J: first published as 10.1136/pgmj.24.267.11 on 1 January 1948. Downloaded from

12 POST GRADUATE MEDICAL JOURNAL January T948 of the nerve and receives regional reinforcements cordant results obtained by Adams might readily here and there. be explained either by destruction of, or damage The view that the circulation within the nerve done to, epineural vessels during manipulation, or might be dominated in particular segments by the perhaps, more likely, to thrombosis within the local nutrient artery has in the past been put for- ligated vessels spreading into the epineural vessels ward, and, were it a fact, would be of considerable or beyond and so involving the longitudinal surgical importance. The extensive mobilizations vascular pathway within the nerve. This sug- of nerves carried out in operations scarcely lend gestion, though speculative, is supported by support to the view, and certain experimental Sunderland ( 1 945, b) who states : ' If the nerve is findings in animals very strongly suggest that the roughly and carelessly stripped from its bed, role of any particular nutrient artery in the supply these delicate channels are likely to be torn .. . of its own region of the nerve is virtually non- interrupting thereby the superficial system on the essential. In this connection Adams (1943) re- surface of the nerve, a disturbance which, in ported that in the rabbit's sciatic nerve the de- turn, is liable to embarrass the intraneural struction of the nutrient arteries in the thigh led circulation.' to negligible degenerative changes in the majority (b) In another series of rabbits the sciatic of the animals investigated; he had, however, a nerve, after mobilization in the thigh and ligation small minority of animals in which quite extensive of all nutrient arteries, was ligatured at the level degeneratiors occurred and this minority, though of the knee. This left the sciatic nerve completely small, left open a doubt as to whether there might devoid of any nutrient supply along its course in be some significant variation in the supply of the the thigh and also it ensured the complete oblitera- nerve in the cases concerned which might have led tion of the longitudinal vascular bed within the to the dominance of one nutrient artery, or, again, nerve at the site of the ligature. Previous experi- as to whether there might not be some other factor ments (e.g., Adams, 1943) had made it clear that coming into play to give the discordant result. the mere ligation of the nutrient vessels did not necessarily lead to any extensive degenerationby copyright. Experimental Study of Blood Supply within the nerve. The object of this series of The writer has investigated the problem from experiments was to take the nerve with its two angles in the rabbit's sciatic nerve. regional sources obliterated and then, in addition, (a) In one series of animals the nerve was embarrass the intraneural circulation by preventing mobilized completely along its course from the the free flow of blood throughout the length of the buttock to the knee and all nutrient arteries segment under observation. The animals were approaching the nerve severed. In addition the allowed to survive for ten days and nerves in the obvious epineural vessels were severed so as to thigh were then examined, either histologically or interrupt, as far as possible, the longitudinal by injection. Those subjected to histology showedhttp://pmj.bmj.com/ system of vessels. The latter procedure, carried that there was invariably degeneration induced out under a dissecting microscope, did not, of within the nerve. The degeneration was never course, affect any vessels running within the massive but it tended to be more extensive in the nerve and could not, therefore, obliterate more more distal parts of the nerve (the segment of the than a proportion of the larger epineural vessels. nerve immediately adjacent to the ligature was The results indicated that on destruction not considered in the assessment of the result). In following those cases which were the nerves were of the epineural vessels there was invariably some injected, on September 23, 2021 by guest. Protected degeneration, varying from case to case, but never subsequently cleared and a comparison made massive, and, in comparison with Adam's results between the injected experimental nerves and (excluding his discrepant findings) the degenera- injected normal nerves. It was found that the tion induced was of a greater order. The escape nerves which had been mobilized and ligatured of the nerve from any obvious degeneration follow- took the injection mass virtually as well as normal ing on the mere ligation of the nutrient vessels nerves except in the lowest segment adjacent to and the invariable production of degeneration on the ligature. These injections were carried out the destruction of epineural vessels, very strongly sufficiently long after the operation, to preclude suggests that the latter are in some way more vital any possibility of leakage from cut vessels, and than the former. It is suggested that by de- suggested strongly that the vascular bed within struction of the epineural vessels some portions of the nerve did not suffer appreciably. the longitudinal capillary bed served by such It may be concluded from the above experiments vessels would be put out of action and the resulting that though destruction of nutrient arteries ap- degeneration explained on such grounds. In this proaching the nerve has little or no effect, destruc- connection it seems not unlikely that the dis- tion of the epineural vissels leads to limited Postgrad Med J: first published as 10.1136/pgmj.24.267.11 on 1 January 1948. Downloaded from

Jnuary 1948 DURWARD: The Blood Supply of Nerves degenerative changes depending on the extent of their conclusions indicated very clearly that all epineural vascular deprivation. The destruction the effects described were attributable to ischaemia of the epineural vessels, it is suggested, destroys and not in any sense to compression of the nerve in part the longitudinal vascular bed of the nerve fibres. More recently, Denny Brown and Brenner and to that extent renders the region ischaemic. (I944) have studied in experimental animals the It is further evident that the arterial and venous effects of graduated pressures induced by spring circulation in a peripheral nerve is adequate to clips. Complete histological examination was maintain an effective circulation, even when a possible and they were able to observe the presence complete through-circulation is denied, as by or absence of degenerative changes in the nerves. ligature of the nerve distally. These findings, of From our viewpoint, the interesting conclusion course, relate to the nerve involved in the experi- was drawn 'that the effect of pressure on the ments and it is quite conceivable that the longer nerve is considered to be due entirely to ischaemia.' lengths of nerve involved in human operations These two sets of observations carried out by might vary the severity of such degenerative very different methods-one in man and the other changes as occur. Seddon and Holmes (I945) in the experimental animal-give the strongest have reported ischaemic damage in the peripheral support to the view that the intraneural vascular stump of the divided median nerve in the upper bed is vital in the normal functioning of the nerve. third of the forearm. In the case concerned the If local pressures induced by clamps or other anterior interosseous artery had been destroyed. mechanisms can induce sensory and motor dis- It would be unusual for the median nerve not to turbances, and even degenerative changes, by receive nutrient vessels in its course through the occlusion of the vascular bed within the nerve, arm (Sunderland, 1945, a) and were such vessels it is obviously conceivable that vasospastic states present and intact, the occurrence of an ischaemic involving nerves may do the same thing. This lesion would be surprising; but there remains has been in the case of the the of variation in the possibility investigated ever-present possibility 8th cranial nerve by Atkinson (1941), and follow-by copyright. individual, and the absence of a nutrient branch ing on his work, Adams and Robinson (194i) to the median nerve in its course through the arm, investigated the possibility of trigeminal neuralgia though unusual, has been recorded. With a being essentially a vasospastic condition. The severed nerve, it would be the lowest segment exhibition of vasodilator drugs did lend some which would show ischaemia, and in the case support to the view that in certain cases at any quoted by Seddon and Holmes, the severance of rate vasospasm within the trigeminal nerve was the anterior interosseous artery in addition was at the root of the sensory disturbance. Whether doubtless the crucial factor in inducing the severe neuralgias are to regarded as commonly due to, or ischaemia. only occasionally caused is a by,, vasospasm, http://pmj.bmj.com/ point on which no final decision may yet be given, Obliteration of Intraneural Vessels by but the experimental evidence suggests that such Pressure a mechanism is by no means unlikely. The effects of local pressure on the circulation From a different approach, the role of the within a peripheral nerve have been studied by circulation within the nerve has been studied by various workers. There are inherent difficulties Bacsich and Wyburn (1945). Their work was in all methods and the occlusion of the carried out on the rabbit's sciatic nerve and

complete on September 23, 2021 by guest. Protected intraneural vascular bed by pressures which would comparisons were made between the regeneration avoid structural damage to nerve fibres, is a matter rate in a nerve with a normal blood supply and a of difficulty, since the vessels lying upon and with- nerve deprived of its regional sources of supply. in the nerve are of varying sizes and, as has been They have concluded that no significant change in pointed out previously, vessels of a considerable the regeneration rate of nerves is attributable to size may course amongst the fasciculi and so experimentally induced variations in blood supply escape occlusion by pressures which would and this lends further support to the view that obliterate capillaries. There is, however, a body the essential vascular bed of the nerve is a con- of evidence derived from observations on com- tinuous longitudinal system, not regionally de- pression of nerves, and two references to such pendent on the nutrient arteries. work may 'be made here. Lewis, Pickering and Rothschild (193I) investigated the effects of the Summary arrested blood flow to a limb in man, by means of Anatomical. Each nerve receives local branches clamps and encircling cuffs. They were primarily of supply from adjacent arteries. Though pre- concerned in the study of the resulting motor and senting the customary variation in their arrange- sensory deficits and the recovery therefrom, but ment, associated with small arteries in general, the C, Postgrad Med J: first published as 10.1136/pgmj.24.267.11 on 1 January 1948. Downloaded from

14 POST GRADUATE MEDICAL JOURNAL January 1948 position of such nutrient arteries is reasonably and more particularly within the nerve is function- predictable. ally more important than any localized group of On the nerve a series of epineural vessels is nutrient vessels. formed, whose branches pass into the perineurium and, finally, there is produced within the fasciculi BIBLIOGRAPHY a longitudinally disposed which ADAMS, W. E. (1942), J. Anat., Lond., 76, 323. capillary plexus ADAMS, W. E. (1943), J. Anat., Lond., 77, 243. is continuous throughout the length of the nerve ADAMS, W. E. and ROBINSON, W. (194I), Lancet, November and is not dominated by local nutrient vessels. 8th, p. 555. The intraneural forms a ATKINSON, M. (1941), J. Amer. Med. Ass., Ix6, I753. Experimental. plexus BACSICH, P. and WYBURN, G. M. (1945), J. Anat., 79, 74. system which is normally reinforced by the local DENNY BROWN, D. and BRENNER, C. (x944), Arch. Neur. & nutrient arteries, but which can function ade- Psychiat., 52, 1. LEWIS, T., PICKERING, G. W. and ROTHSCHILD, P. (1931), quately in a given length of nerve even when the Heart, 16, I. local branches are ligated. SEDDON, H. J. and HOLMES, W. (1945), Brit. J. Surg., 32, 389. of or intraneural vessels SUNDERLAND, S. (1945), (a) Arch. Neur. & Psychiat., Chicago, Obliteration epineural 53, 91. produces degeneration of varying degree depend- SUNDERLAND, S. (1945), (b) Arch. Neur. & Psychiat., Chicago, on the extent of vascular 54, 280. ing deprivation. SUNDERLAND. S. (1945), (c) Arch. Neur. & Psychiat., Chicago, The complete and intact system of vessels upon 54, 283.

CONFUSIONAL STATES IN ACUTE DISEASE by copyright. By J. M. NAISH, M.D., M.R.C.P. Tutor in Medicine, University of Bristol.

Many a patient's battle to overcome an acute The physical manifestations are restlessness, in- disease is lost because, failing to stand the strain somnia, incontinence and anorexia; examination of the illness, he becomes delirious. The additional usually shows some pyrexia and tachycardia, a burden thrown upon his body by restlessness, fear, furred tongue and slurring of the speech. and failure to obey those trying to help, is sufficient The mental changes vary from one moment tohttp://pmj.bmj.com/ to tip the balance against him. The problem the next. The changing form of the mental which such cases present is a common one, and, picture is perhaps the most typical finding in lying in the no-man's-land between general delirium and is due to the extreme suggestibility medicine and psychiatry, does not receive the of delirious people whose moods and behaviour attention which it needs. are swayed both by their physical surroundings and their attendants. The prevailing delirious Classical Delirium mood, however, is one of fear and horror; their There is nowhere any sharp dividing line be- speech abounds with talk of struggles, crises and on September 23, 2021 by guest. Protected tween the full-blown picture of severe delirium bankruptcy. Restless activity and complete in- and the mild nocturnal confusion of thought so somnia dominate the picture. frequently found in ill people. The delirious are not only prone to invent, or to Many patients, particularly the elderly, become elaborate the truth in a broken sort of way, but confused when their illness is at its height. This they misinterpret their present surroundings and confusion and lack of grasp, always at its worst instructions. Essentially, this inability to interpret nocturnally, may lead them to get out of bed in or understand the present has the same roots- the belief that they should be going out to work, failure of memory, concentration, and mental or to put their shoes on beneath the sheets to keep grasp-as the tendency to invent the past. They their feet warm. They are often shamefaced in the can only do the simplest and shortest test problems morning and attribute their experiences to a bad because they cannot hold their brains to the task dream. for more than a few moments at a time. It is Fully developed delirium leads to well-defined true to say, however, that some delirious patients physical and mental changes in these patients, and can, by a superhuman effort of will, achieve mental these should be kept clearly in mind. clarity when circumstances urgently demand it.