SYNONYM.—External pachymeningitis.
ETIOLOGY.—The most frequent causes of external pachymeningitis are injuries to the cranial bones from violence, caries and necrosis of the same, and concussion from blows on the head. Next in order of frequency, if not even more common, comes the propagation of inflammation from disease of the inner ear and of the mastoid cells. It is only of late years that this important subject has been brought prominently forward and the danger of ear diseases in this respect fully pointed out. The channels of communication, as indicated by Von Tröltsch1 in his valuable article on diseases of the ear, are along the arteries and veins which pass from the skin of the meatus and the mucous periosteal lining of the middle ear to the contiguous bone, while the capillaries of the petrous bone are in direct connection with the dura mater, so that the vessels of the latter are in communication with the soft parts of the external and middle ear. The vessels of the ear and the membranes of the brain are also directly connected through the diploëtic veins of the temporal bone, which discharge into the sinuses of the dura, as well as through the venæ emissariæ, which, arising from the sinuses, pass through the bone and discharge their contents into the external veins of the head. Von Tröltsch also points out that the extension of an inflammatory process may occur along the sheath of the facial nerve, the canal of which (canalis Fallopii) is a branch of the internal auditory canal and is lined by the dura mater. The latter is separated from the mucosa of the tympanum only by a thin, transparent, and often defective plate of bone. Inflammation may also be transmitted from the scalp by means of the vessels which pass through the bones of the skull. In this way erysipelas and other diseases of the integument sometimes give rise to external pachymeningitis.
1 “Die Krankheiten des Gehörorganes,” von Anton von Tröltsch, in Gerhardt's Handb. der Kinderkrankheiten, Tübingen, 1879, 5 B., ii. Abt., p. 150; also English translation of the same, by J. O. Green, M.D., New York, 1882, p. 107.
SYMPTOMS.—There are no known symptoms which are characteristic of inflammation of the external surface of the dura. In cases of death from other diseases an autopsy may show traces of previous inflammation, such as thickening of the membrane and its firm adhesion to the cranial bones, which were not manifested during life by other symptoms than those which accompany meningeal disease in general; and in some instances none at all were known to have occurred. At a variable time after the receipt of an injury to the head the patient may complain of headache, followed by a chill, with high fever, vomiting, vertigo, delirium, unconsciousness, convulsions, etc., arising from compression by the products of inflammation. The same phenomena may follow the transmission of inflammation to the dura from caries or other disease of the bones, or from otitis medea purulenta. These symptoms usually continue without interruption, though there is sometimes more or less complete remission of the pain, and the patient may recover his consciousness for a time, thus giving rise to fallacious hopes. In a large proportion of cases the disease extends to the inner surface of the membrane and to the pia, without any noticeable change in his condition other than coma. In chronic external pachymeningitis the principal symptom is pain in the head, which may persist for weeks or months without other manifestations except drowsiness. Sometimes, on the contrary, there is obstinate vigilance. Mental symptoms, such as loss of memory, hallucinations, dementia, or mania, are sometimes noticed, ending, as in the acute form, in coma.
PATHOLOGICAL ANATOMY.—In chronic cases often nothing is found but thickening of the membrane, which generally becomes firmly united to the inner surface of the cranium. Indeed, these appearances are not unfrequently observed, to a limited extent, when there has been no history of disease to account for them. In other chronic cases the connective tissue of the membrane is found to be in part ossified, and the osteophytes of the cranium sometimes found in pregnant women and in patients with rheumatic cachexia are supposed to be due to a chronic inflammatory process of the dura. The first changes observed in acute external pachymeningitis are increased vascularization, shown by red lines corresponding to the blood-vessels, with punctiform extravasations, swelling, and softening of the tissue. Later, there is thickening of the membrane from new formation of connective tissue, and exudation of lymph, and sometimes of pus, which latter may accumulate between the dura and the cranial bones, or in traumatic cases may escape through openings in the skull. The dura and the pia become united in most cases of acute inflammation. The lateral sinuses frequently contain thrombi, which, when ante-mortem, are firm in structure, reddish-brown in color, often closely adherent to the walls of the vessel, and may extend to other veins, sometimes reaching as far as the jugulars. When purulent inflammation of a sinus occurs, its walls are thickened, softened, and discolored, and the inner surface is roughened. The thrombus becomes more or less purulent or sanious, disintegrates, and the infecting particles are carried into the circulation, giving rise to embolism and disseminated abscesses of the lungs, kidneys, liver, or spleen. Other lesions, such as injury or caries of the cranial bones and purulent inflammation of the middle ear and of the mastoid cells, are frequently found in conjunction with pachymeningitis, to which they have given rise. When the disease of the dura extends to the pia, the adjacent portion of the brain is often found implicated in the inflammation. In traumatic cases the dura may be detached from the bone and lacerated to a greater or less extent.
DIAGNOSIS.—The existence of external pachymeningitis may be suspected from cerebral symptoms following traumatic injury of the skull, erysipelas, or suppurative otitis medea, but apart from the etiology it would not be possible to distinguish it from internal inflammation of the membrane, or even from leptomeningitis.
PROGNOSIS.—In cases of suspected external pachymeningitis the prognosis will depend upon the evidence of effusion of pus or blood between the dura and the skull, and the possibility of their removal. A large proportion of cases are fatal, especially those arising from caries of the cranial bones and from the propagation of disease from the middle ear, the mastoid process, or the external surface of the skull, the inflammation extending through the membrane to the arachnoid surface of the dura, and also to the pia mater. This would be shown by a high temperature, rapid pulse, pain, and delirium, followed by coma and perhaps convulsions. The frequency with which external pachymeningitis occurs in connection with diseases of the ear should put the physician on his guard in cases of otorrhœa or pain in the ear, that he may warn the patient or his friends of the possibility of danger, and may employ an appropriate treatment.
TREATMENT.—In all cases of injury to the skull or of severe concussion the possibility of subsequent external meningitis should be borne in mind. The patient should be confined to the bed and be carefully secluded from excitement. Cold applications should be made to the head, the diet should be simple and somewhat restricted, and the bowels kept free without active purging. If there be evidence or suspicion of the presence of pus or of blood between the dura and the skull, means should be taken to evacuate the effusion. In case of inflammatory symptoms leeches should be applied behind the ears, and a stimulating liniment or croton oil rubbed on the scalp. There is no specific treatment. Pain and sleeplessness must be relieved by opiates and sedatives, and the strength must be sustained by nourishing diet and stimulants.
Internal Pachymeningitis.
Internal pachymeningitis is of two kinds: 1st, simple inflammation, which may be accompanied by purulent exudation and by a corresponding affection of the pia mater: 2d, hemorrhagic inflammation or hæmatoma of the dura mater. Simple inflammation of the internal or lower surface of the dura, without the coexistence of external pachymeningitis is rarely found in the adult. The morbid appearances differ but little from that of the external form, and the causes and the diagnosis are also similar. In children, however, it is not uncommon, according to Steffen.2 The pus may discharge itself spontaneously through the fontanels or the sutures, or caries of the cranial bones may open a passage for its exit. It has also been evacuated artificially when the symptoms have indicated its presence. In other cases more or less extensive firm adhesions between the dura and pia mater have shown the previous existence of inflammation, but it would be difficult to say in which membrane it began. In some instances no symptoms are observed during life; in others the coexistence of inflammation of the pia, effusion into the ventricles, etc. prevent an exact diagnosis.