J R Army Med Corps: first published as 10.1136/jramc-102-03-01 on 1 July 1956. Downloaded from VOL. 102 JULY, 1956 No. 3 Vol. 102, No. 2,was issued on 25th June, 1956 Authors are alone responsible for the statements made and the opinions expressed in their papers. Journal of the Royal Army Medical ,Corps THE, CAUSES AND CHARACTERISTICS OF CHRONIC guest. Protected by copyright. BENIGN HEADACHE IN SOLDIERS OBSERVATIONS ON HEADACHE NOT .ATTRIBUTABLE TO SERIOUS , PHYSICAL OR MENTAL DISEASE BY D. E. MARMION, M.A., M.D.(Camb.), M.R.C.P. Major, Royal Army Medical Corps (Retired) HEADACHE is a symptom ubiquitous in both civil and military medical practice, and is a common and troublesome problem Jor the regimental medical officer and the medical specialist. No apology is therefore needed for an attempt to examine the subject from the standpoint of the military physician. A proper comprehension of the causes and characteristics of headache is http://militaryhealth.bmj.com/ impossible without some knowledge of the relevant anatomy and physiology, and as much of this is barely touched, upon in current teaching in this country it will be necessary to summarize it. THE ANATOMY AND PHYSIOLOGY OF HEADACHE ~eadache is ~sentially pain in the head, and pain may be "felt" in a part of the body for one or more of several reasons, which are summarized in Table 1. h is outside the scope of this article to' consider in greater detail the physiology of pain, though some understanding of it'is essential for the intel1igent 'practice on September 28, 2021 by of medicine; A good brief account of aspects of it relevant to the present topic will be found in Fletcher's Medical Disorders o/the Locomotor System (Fletcher, 1951).; , " :Not all- the structures_ of the head. and' neck are pairi~sensitive. Outside the 167 J R Army Med Corps: first published as 10.1136/jramc-102-03-01 on 1 July 1956. Downloaded from 168 Chronic Benign Headache in Soldiers cranial cavity, the skin, subcutaneous tissues, arteries, most nerves, -muscles, tendons, aponeuroses, the eye and orbital contents, the mucous membranes of the oro-nasal cavities, the teeth and the jaws are in varying degrees pain-sensitive; the superficial veins, the cranial bones and diploe are insensitive or nearly so. Within the cranial cavity the dural- floors of the anterior and posterior fossre, the dural venous sinuses and their larger tributaries, th~ arteries at the base bf the brain, their larger branches, the meningeal arteries and the dura in their tmmediatevicinity, and some cranial ~erves (V, VII, IX, X, XII) are pain­ sensitive. The rest of the dura, the pia-archnoid, the smaller intracranial vessels, the ependyma and choroid plexuses, the parenchyma of the brain a~d the other cranial nerves are insensitive. - - . Supratentorial structures are innervated by the trigeminal nerve, and pain arising in them is referred to various sites in the anterior half of the head. Infra-. tentorial structures are innervated by the -last four, cranial nerves and the first three cervical, and pain from them is referred to the posterior half of the head j the subocciput and the upper part of the neck. The exact sites of reference from many intracranial and extracranial situations_ have been worked out experi­ mentally with great ingenuity by Wolff (1948) and his colleagues, and other guest. Protected by copyright. workers, but for a variety of reasons much of this information is of limited value t-O the clinician. The forms of stimulation that give rise to pain in extracranial structures are in general familiar enough to require no special mention, except to draw attention_ to the importance and peculiarities of the arteries and muscles, which will receive detailed attention later. Within the cranium distortion is the main pain-produc­ ing stimulus. Traction upon large vessels and sensitive dura, or over-distension or excessive pulsation of large arteries are examples. Inflammation, as in meningitis, and chemical irritation by blood or air -introduced into the sub:':'_ arachnoid space, may also cause pain ; raised or lowered intracranial pressure of itself does not, except in so far as it causes or permits distortion, as in the headache following lumbar puncture (Pickering, 1949). This explains the well-known fact that it is possible to· have greatly increased intracranial pressure without http://militaryhealth.bmj.com/ headache. We must noW proceed to consider more carefully the principal mechanisms­ involved in the productiori of benign headache. Vascular headache Overdilatation or excessive pulsation of intracranial o~ extracranial arteries is by far the commonest cause of headache (Pickering, loco cit.). The "ordinary" headache of universal experience, whether from emotional causes, acute infec­ tion, a blow on the head or alcoholic excess, is for the most part and in most cases the result of excessive pulsation of cranial arteries, especially those within the on September 28, 2021 by cranial cavity; though the exact mechanism is obscure, it is clear that somehow_ there is disproportion between the intra-arterial blood-pressure and the pressure of the extra-arterial supporting structures (within the cranium this may be regarded as equivalent to the cerebrospinal fluid pressure), so that the relatively J R Army Med Corps: first published as 10.1136/jramc-102-03-01 on 1 July 1956. Downloaded from D.E. Marmion 169 unsupported arterial wall dilates and pulsates, causing pain by stretching the periarterial nerve plexus. This state of affairs can be reproduced experimentally, by giving an injection of histamine .. Hence this type of headache is sometimes called the histamine-type in contradistinction to the predominantly extracranial migraine-type referred to· below. The resulting throbbing headache is im­ mediately relieved by intrathecal injection of fluid to raise the cerebrospinal fluid pressure. In migraine and arterial hypertension, the extracranial arteries are especially affected, and it is common to see the superficial temporal' arteries ·standing out and pulsating violently. Firm pressure on this artery in front of the auricle will relieve the pain (though not in the later stages when the vessel wall is also redematous). But even in classical migraine the intracranial arteries are involved to some extent, and the distinction between intracranial (histam!ne-type) and extracranial (migraine-type) headache is by no means firm. Headache from distortion of intracranial structures Space-occupying lesions, scars, adhesions and foreign bodies cause displace.,. ment and distortion of intracranial structures and hence may give rise to pain. guest. Protected by copyright. Table 1. Pain mechanisms and pathways l\i1echanism Physiology Common Example Headache EXample· Direct Pain felt at site of noxious Pain of cut finger Temporal headache in stimulus. felt at site of cut. temporal arteritis. Referred Pain referred from site of noxious Shoulder-tip pain in Supra-orbital headache stimulus to another site of diaphragmatic in internal carotid an­ similar segmental innervation. pleurisy (both C4). eurysm (both trige­ minal). Spread Noxious stimulus causes excita­ Crush injury of one Toothache. in· upper tion of sensory neurons, with finger causes pain in jaw spreads to face "overflow" of excitation to other adjacent fingers, or and head if severe neurons in same and neighbour­ even hand and arm . (trigeminal). ing segments, so that pain ap­ (cervical and thoracic pears to spread .to areas inner­ segments). vated by those neurons. http://militaryhealth.bmj.com/ Muscular Noxious stimulus causes reflex Pain, tenderness and Occipital headache .in spasm of muscles innervated by spasm of loin mus­ upper cervical arth­ involved segment: persistent cles in kidney disease ritis (C2-3). spasm of muscles causes pain (thoraco-Iumbar seg­ and tenderness. ments). Neurogenic Disorders of neural pathways and Neuritis, herpetic Occipital, supra-orbi­ centres subserving pain sensation neuralgia, thalamic tal,. etc.; neuralgia. i.e. nerve, posterior root and syndrome, etc. ganglion, posterior horn, spino­ thalamic tract, thalamus (and homologous cranial nerve struc­ tures and connexions). on September 28, 2021 by Psychogenic Pain exists only in sensorium "Cardiac" pain in Some types of hyste­ (i.e., is "suprasegmental") and neuro-circulatory rical headache. has no physical basis at the asthenia (effort syn­ periphery. drome). J R Army Med Corps: first published as 10.1136/jramc-102-03-01 on 1 July 1956. Downloaded from 170 Chronic Benign Headache in Soldiers Clinical examples are legion. Minimal displacement of structures consequent upon withdrawal of cerebrospinal fluid is probably also a factor in the pathogenesis of post-lumbar puncture headache. On more commonplace ground, the ag­ gravation of almost,any headache by jolting or violent shaking of the head is due to the inertia of the cranial contents causing them to drag\lpon their anchorages, whose pain-threshold is already lowered by pre-existing headache. '. Neurogenic and neuralgic headache It is a common observation that a patien~ with a neuralgia of the head usually complains of "pain in the head" rather than "headache." In fact neuralgic pain is different from the famiiiar, if indescribable, pain of headache, even though. the two may oh. occasion coexist: as when neuralgia causes' secondary muscle spasm and consequent muscular he~dache. .' Neuralgia may occur in several cranial nerves (particularly V, VII, and IX) and the cervical nerves, and possibly in association with some