SPONTANEOUS VENTRICULAR RUPTURE IN HYDROCEPHALUS,WITH SUBTENTORIAL CYST FORMATION

BY

JOE PENNYBACKER and DOROTHY S. RUSSELL *

(From the Nuffield Department of Surgery, Oxford)

(RECEIVED 9TH APRIL, 1943)

The anatomical features of hydrocephalus are fairlywell known, and a growing knowledge of thepathology suggests that in most if not all cases theventricular dilatation can be explained by obstructionto the circulation of the cerebro-spinal fluid. It isnot always easy to identify the site or cause of theobstruction, but a common place is in the narrows ofthe midbrain where the aqueduct may be compressedby a benign proliferation of the subependymal gliaor by a tumour of the brain stem, pineal gland orvermis cerebelli. As the prognosis and treatmentdiffer considerably in these various conditions, wecommonly look to ventriculography for help indiagnosis. For various reasons, the interpretationof air shadows in this region is not always easy, orindeed possible, and we feel that any additionalinformation about the pathological possibilitiesshould be of importance.

This report deals chiefly with two cases of hydro-cephalus in which the dilatation of the lateral ventri-cles was accompanied by rupture of the wall of theventricle in the region of the vestibule, and theformation of a cyst-like space under the tentoriumcommunicating with the lateral ventricle. The siteof the rupture was identical in the two cases, and theventriculographic appearances were similar. Inboth cases the hydrocephalus resulted from aqueductobstruction, in one by proliferation of the sub-ependymal glia and in the other by a fibrillaryastrocytoma of the brain stem. We have alsoincluded the pathological report of a case of hydi c-cephalus due to adhesive arachnoiditis in which anearly stage in the development of this process wasseen.Our interest in this abnormality began with an

earlier case of stenosis of the aqueduct which hadproduced great dilatation of the third ventricle.The distended suprapineal recess protruded as acyst-like swelling beneath the splenium, insinuatingitself between the lower surfaces of the occipitallobes, and the upper surface of the cerebellum.Since then we have seen such dilatations in ventri-culograms on a number of occasions and had cometo regard the presence of a large suprapineal recessas evidence for an intrinsic lesion of the brain stem(benign stricture or tumour) as opposed to anextrinsic lesion such as a tumour of the superior

vermis or of the pineal gland. The recess may bedilated in cases of obstruction in the distal part ofthe fourth ventricle too, but in these cases theaqueduct and fourth ventricle are generally dilatedand it is fairly easy to demonstrate them in ventri-culograms. In our first case, a large air-shadowbeneath the tentorium was thought to be such adilated suprapineal recess until it was shown atnecropsy to be in communication with the lateraland not with the third ventricle.

Case ReportsCase 1. J.H. (R.I. 11851), a girl of 16 years, was

admitted to the Radcliffe Infirmary on 4/11/40, com-plaining of headache. For two years she had beensubject to attacks of headache lasting for four or fivehours, occurring once or twice a month, with good healthin the intervals. She occasionally vomited with theheadaches, and for a year she had often been aware of arhythmical noise in the head (which it was found could bestopped by compressing one or other carotid artery in theneck). The increasing frequency and severity of theheadaches brought her to hospital; there were no othersymptoms on direct enquiry.On examination she was a healthy-looking girl nor-

mally developed and rather above the average intelli-gence. The skull was 54 cm. in circumference, slightlylarger than normal. There was bilateral papillcedema,3 D., but the visual acuity and fields were normal, exceptfor slight enlargement of the blind spots. The pupilsand ocular movements were normal, and there were nodefinite abnormalities in the examination of the rest of thenervous system. The spinal fluid pressure was 270 mm.,and the fluid was normal on analysis. X-rays of theskull showed some convolutional thinning of the vault,early separation of the sutures, and some erosion of thesella turcica.

Comment.-This was thus a case of increasedintracranial pressure with no definite localizingsigns. Ventriculography revealed symmetrical dila-tation of the lateral ventricles, and of the thirdventricle with what was interpreted as a dilatedsuprapineal pouch (Fig. 1). The aqueduct couldnot be visualized distal to its upper end, and no airhad got through to the fourth ventricle or cisternamagna. The appearances were regarded as beingdue to a stricture of the aqueduct, probably causedby proliferation of the subependymal glia.At operation on the same day, 8/11/40, an incision

was made in the lamina terminalis, by way of theright sub-frontal approach. The post-operative

Workiing for the Medical Research Council.

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period was uneventful, and she was discharged fromhospital on 28/11/40 free from symptoms. Theosteoplastic flap was not tense, the spinal fluid pres-sure was 160 mm., and the papillkedema hadvirtually subsided.

She was well for two months, when she had a boutof pain in the right upper jaw which was eased by adental extraction. At this time, the decompression

Fig. I.-Case 1-First ventriculogram, showing smallpouch below lateral ventricle.

was apparently flat, but as the pathological diag-nosis had not been verified, we advised a course ofdeep X-ray therapy to the region of the brain stem.From the beginning of the treatment the decompres-sion became more tense, the flap bulged, she de-veloped a gradually progressive left hemiplegia,became very drowsy and incontinent. In that stateshe was readmitted on 6/5/41, 6 months after opera-tion.

Clearly the fistula had not been effective, or, if it

had, the lesion had progressed beyond the limit ofcompensation. The ventriculogram was repeated,and the ventricular dilatation was even morepronounced. The right frontal horn bulged withthe decompression; but more striking was a largecystic collection under the anterior border of thetentorium (Fig. 2). This was an advanced stage ofwhat had been seen six months earlier and had beenregarded as a dilated suprapineal recess. Again noair was seen distal to the upper reaches of theaqueduct.As the anterior fistula did not seem to have been

effective, and as the presence of this pouch in theposterior fossa seemed to be an argument against aneoplasm in the cerebellum, we decided to open thepouch from behind, a sort of posterior ventri-culostomy, hoping that a fistula between the thirdventricle and the cisterna ambiens might be effectivewhere one between the third ventricle and cisternachiasmaticus had failed. By the usual cerebellarexposure, and retraction of the left cerebellar lobedownward from the tentorium, the cyst-like dilatationwas seen and incised (Fig. 3). Although it waspossible to explore the interior of this cavity bydirect vision, the relations were confusing andanatomical landmarks could not be identified withcertainty.

Again the post-operative phase was encouraging.Her general condition improved, the hemiplegialessened, and the intracranial pressure, as judged byrecession of the decompression and normal cere-brospinal fluid pressure, was satisfactory. On themorning of the ninth post-operative day she hadtwo Jacksonian epileptic attacks down the left sideof the body in quick succession, and died suddenly.

Pathological ExaminationSummary of Necropsy.-Congestion of lungs.

Internal hydrocephalus. Gliosis of iter. Opera-tion: Ventriculostomy.

Bilateral pleural effusion (42 pint each side).Congestion of lungs; collapse of basal portions of

Fig. 2.-Case I -Ventriculograms made 6 months later, showing increased size of cyst.

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JOE PENNYBACKER AND DOROTHY S. RUSSELL

-.~~-

Fig. 3. Case I Operation sketch.

lungs. Slight fibrous thickening of base of cusps ofmitral valve. Calculous material in pelvis of leftkidney; no further abnormality in abdominalorgans. A few small cysts in colloidal thyroidgland.

Brain. Macroscopic. The cerebral hemispheres wercconsiderably but unevenly expanded, the right frontal

lobe bulging greatly at the site of the old craniotomy,which measured 8 by 4-5 cm. Apart from this areathe meninges over the convexities of the brain appearednormal, except for slight subdural and subarachnoidhzemorrhage over the inferior surface of the righttemporo-occipital region. In the meninges over thequadrigeminal plate was an empty space which measured19 cm. from above down by 1 1 cm. in the mid-sagittalplane by about 2 2 cm. from side to side, and was boundeddorsally and laterally by a grey translucent fibrousmembrane continuous with the arachnoid membrane.The roof of the space arched over the gap between thesplenium and the anterior border of the vermis, lyingbeneath but in close relationship to the pineal body andthe great vein of Galen (Fig. 4). An operative perfora-tion, measuring 0 7 cm. in diameter, occupied the leftside of the membrane. Internally the membraneappeared smooth and was sealed off everywhere from theadjacent cerebrospinal spaces, except at one point whereit communicated with the left lateral ventricle by anorifice measuring 0 8 by 0 5 cm. This orifice was situatedin the hinder part of the body of the ventricle, in the thinlamina of white matter that lies posterior to the fornixand medial to the hippocampal gyrus (Fig. 4). Itsborders were smooth and rounded. At the same positionin the right lateral ventricle was a dimple of similar size,but with no perforaticn in its depths. A ventriculostomy

(Top portion).

(Bottom portion).Fig. 4.-CCase 1-Sketch showing relations of cyst, aperture into left ventricle, and thinning of the corresponding

part of the right ventricular wall.

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VENTRICULAR RUPTURE IN HYDROCEPHALUS

opening, measuring 04 by 0-3 cm., was present in thesupraoptic recess. Delicate fibrous adhesions wereattached to the borders of this opening, and the ruptureof some of these during removal of the brain was followedby a gush of clear cerebrospinal fluid.

There was considerable dilatation of the third andlateral ventricles, the foramina of Monro being 0-8 cm.in diameter on either side. The right frontal horn wasmore voluminous than the left. The septum pellucidumwas considerably fenestrated and the grey commissureelongated (1 2 cm.). The ependyma everywhere ap-peared thick and corrugated, but was smooth, glistening,and free from granulation. The choroid plexusesappeared normal. No lumen was visible throughoutthe anterior 0-6 cm. of the iter. The fourth ventricle wasnormal.

Microscopic. The mid-brain was divided into fourslices in the coronal plane and these, with the anteriorend of the vermis in the mid-sagittal plane, the postero-lateral border of the orifice in the left ventricle and por-tions of the third and fourth ventricles in the coronalplane were embedded in paraffin wax. Sections werestained with Ehrlich's hematoxylin and eosin, Weigert'siron hamatoxylin and Van Gieson's mixture and withphosphotungstic acid hamatoxylin.The lumen of the itel- is subdivided into a number of

small irregular channels by a dense cellular and fibrillarygliosis which extends into, without expanding, thequadrigeminal plate, diminishing towards its dorsalsurface but becoming intensified again in the marginal glia.The gliosis encroaches ventrolaterally on thie borders ofthe nucleus of the third nerve on the left, but the rightnucleus is free. The greater part of the iter is so involved,and even where at either end of its course the lumen is ofnormal outline there is excessive thickening of the dorsalsuLbependymal glia extending into the quadrigeminalplate. In most places the subdivisions of the lumen arelined with a well-preserved, ciliated ependyma; a fewareas are denuded. A few blood vessels in and near thehyperplastic glial tissue show slight cuffing with smalllymphocytes.The border of the orifice in the left lateral ventricle is

formed by an everted tapering fringe of the subependymalglia which is of normal appearance. The ependymacovering the fringe and the adjacent wall of the ventricleis absent in many places. Over some of the denudedareas there are groups of degenerating leucocytes andmacrophages containing red corpuscles; occasionalmacrophages containing iron pigment occupy the super-ficial layers of subependymal glia. The adjacent lepto-meninges are thickened by young fibrous tissue andsparsely infiltrated with lymphocytes, desquamatedarachnoid cells, and neutrophil leucocytes. At a littledistance from the orifice, corresponding to the margin ofthe space in the cisterna ambiens, there is an abruptchange to normal. A similar thickening and infiltrationaffects the meninges walling this space over the quadri-geminal plate and the anterior border of the vermis.

Short strips of the ependyma of the third ventricle aremissing in some areas, and in other places there is focaldegeneration and necrosis of a few contiguous cells,such points often being overlaid by a small cluster ofmacrophages containing red corpuscles together withdegenerating polymorphonuclear leucocytes and eosino-phil cellular debris. At some of the denuded spots thesubependymal glia protrudes slightly towards the lumen.The appearances suggest an early stage of granularependymitis. In the fourth ventricle the ependyma is ofnormal appearance. The leptomeninges over the brainsteni are sparsely infiltrated with desquamated arachnoidcells and neutrophil leucocytes, and contain some freered corpuscles.

Summiiiiiarv. The hydrocephalus in this case wasdue to gliosis of the iter. As in other similar casesthere was no histological evidence pointing to thextiology of this condition. The scanty perivascularlymphocytic infiltration seen in a few vessels in and

near the gliosis was probably in direct associationwith the slight chronic inflammation of the adjacentmeninges. This infiltration doubtless resulted frombreaking down of tissue at the site of the communica-tion between the left lateral ventricle and theleptomeninges over the quadrigeminal plate. Sub-sequent operative procedures, with the freeing ofred corpuscles and small amounts of cellilar debrisinto the cerebrospinal fluid promoted a slightmeningeal and ependymal reaction as seen over thebrain stem and the lining of the third ventriclerespectively.

Case 2. B.B. (R.I. 16954), a female aged 20 years, wasadmitted on 25 7,41, complaining of severe headache.For two years she had been subject to attacks of head-ache and vomiting, coming on in the early morning,lasting for several hours, and then clearing up com-pletely. These headaches occurred almost daily, withrare intervals of freedom up to a fortnight, and they madeit necessary for her to give up her career of nursing. Ashort time before admission she had had two or threcespecially severe attacks in which the headache wasaccompanied by a transient loss of contact with hersurroundings, a feeling of weakness of all her limbs, andsome difficulty in speaking, which was probably a dysar-thria. The only other symptom of significance was inconnection with menstruation: the menarche occurred at16 years and she had had only three scanty periods fromthat time.On examination, she was a tall young woman with the

facial appearance of mild acromegaly, but there was noenlargement of the hands or feet. The secondary sexualcharacteristics were normally developed. She was alertand intelligent, and during the week of observation inhospital she complained of very severe headache, andvomited on three occasions. There was no enlargementof the skull. The sense of smell was impaired in eachnostril, but it was not lost. There was bilateral papillo-dema of three diopters, but the Visual actiity and fieldswere normal, except for slight enlargement of the blindspots. The pupils and ocular movements were normal,but there were a few nystagmoid jerks at the extremes oflateral dc 'iation. There was no definite weakness,tremor, or ataxy in her face, trunk, or limbs. Thereflexes were all normal and there was no sensory defect.Lumbar puncture revealed clear, colourless spinal fluidunder a pressure of 300 mm. The fluid contained30 mgm. of protein and no cells. X-rays of the skullshowed some convolutional thinning, early separation ofthe sutures, and gross erosion of the sella turcica.

Comlmeetit. As in the first case, the problem wasone of increased intracranial presstire withoutlocalizing signs, and ventriculography revealedgross ventricular dilatation with a large pouchextending backwards under the tentoriuL1m (Fig. 5).No air was seen distal to the tipper part of theaqueduct.

This appearance was recognized as being similarto that described in Case 1, and the same kind ofprocedure was decided on-i.e., cerebellar decom-pression and incision of the cyst below the tentorium.This operation was done under general anmesthesiawithotit incident. She died seven hotLrs later froma large extradtl-al h:morrhage over the rightcerebral hemisphere.

Pathological ExaminationSu,nnnar,' of Necropsy,. Extradural haematoma.

Internal hydrocephalus. Astrocytoma of mid-

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A.,"-

Fig. 5. Case 2 ventriculograms showing outlines of cyst below tentorium and aperture into left ventricle.

brain. Operations: suboccipital craniotomy andventriculography.

Recent hematoma, measuring 12 cm. antero-posteriorly by 9 cm. above down and up to 2 5 cm.deep between dura and cranium over right fronto-parietal region, apparently caused by rupture ofvein emerging from dura in region of one of thelacunxe laterales. Slight flattening from abovedownwards of otherwise normal pituitary body.No further abnormalities in endocrine system. Afew atretic follicles and no corpora lutea in ovaries.Atrophy of endometrium in rather small uterus(body 3 cm. long; cervix 2 8 cm. long). Slightcongestion and parenchymatous degeneration ofliver. A few acute erosions (1 5 by 1 cm.) inoesophagus. Slight atheroma involving mitral valveand aortic ring. Slight dilatation and hypertrophyof both ventricles of heart. Subendocardialhemorrhages in left ventricle. Moderate congestionand oedema of lungs. A well-developed, slightlyadipose woman.

Br-ain.-Macr-oscopic.-The hematoma had causedgreat flattening of the right cerebral convexity, but the leftcerebrum was of good shape, its contours being full androunded. The floor of the third ventricle formed atranslucent balloon filling the interpeduncular space andmeasuring 3-0 by 2-2 cm. There was a cerebellar pres-sure-cone 2-0 cm. long. Over the quadrigeminal platethe arachnoid membrane was elevated to form a space,about 3 0 cm. in diameter, which extended over theanterior end of the vermis for a distance of about 2 cm.The membrane contained several oval openings, corres-ponding to those made at operation. Elsewhere thespace appeared to be sealed off from the cerebrospinalpathway, except where an oval orifice, 1 0 by 0-7 cm., ledinto the cavity of the left lateral ventricle in a positionidentical with that observed in Case I (Fig. 6). Therewas no corresponding opening or dimple on the rightside, but the tissue here was thin and translucent. Themargins of the orifice were smooth and rounded, exceptalong its medial border, which was occupied by a cres-centic flange of translucent tissue up to about 2 mm. wide.Both lateral ventricles were equally and considerablydilated, the foramina of Monro measuring 1 5 by I cm.The septum pellucidum was fenestrated. The ependymaeverywhere was somewhat thickened and discoloured byhxemolytic staining. In places there were small abrasions

and recent subependymal hemorrhages resulting frompuncture wounds, especially in the occipital horns.On section the quadrigeminal plate was expanded into

a smooth, dome-shaped mass, about 1 5 mm. dorsi-ventrally and 2 cm. from side to side, of poorly definedrubbery milky-white tissue. The mass involved the rightside rather more than the left. The whole length of theiter was greatly compressed and displaced ventrally andto the left. The pineal body was intact and lay in thedorsal wall of the meningeal space over the mid-brain.The fourth ventricle was normal.

Microscopic-.The tissue examined and stains usedwere as in Case 1. The quadrigeminal plate is greatlyexpanded by a tumour composed of fibrillary astrocyteswhich form, in many places, interlacing bundles ofelongated bipolar cells and elsewhere less dense areas inwhich small stellate cells form small groups separated bya feltwork of their interlacing processes. In the depthsof the mid-brain the tissue is often more cellular, thenuclei being in general larger and uneven in size. A fewmultinucleate cells are present. The borders of thetumour are moderately defined through the circumferen-tial arrangement of the cells in these parts. There isextensive invasion by tumour cells of the leptomeningesover the dorsal surface of the mid-brain and a similarinvasion of the Virchow-Robin space of some of theperforating vessels in this region. On the left ventro-lateral border of the tumour the aqueduct is deformed toan oblique slit. Its ependyma has been partly replacedby tumour cells.The appearances of the orifice in the left lateral ventricle

are similar to those described in Case 1. The corre-sponding imperforate area in the right ventricle isoccupied by a lamina, about 0-6 mm. thick, of ependymaand subependymal glia. The appearances of thenervous tissues are normal, apart from loss of theependymal cells in many areas. There is slight fibrosisof the adjacent meninges with a considerable collection ofred corpuscles, fibrin and few neutrophil leucocytes inthe meshes of the pia. The leptomeninges forming thewall of the cystic space over the mid-brain show fibrousthickening and sparse infiltration with lymphocytes anddesquamated cells as in Case 1. There is, in addition,some infiltration with neutrophil leucocytes. Over theventral aspect of the brain stem the reaction is limited toslight focal leuLcocytic infiltration.

Summary.-This case resembles Case I in theformation of an opening between the left lateralventricle and the leptomeninges as a mechanicalconsequence of internal hydrocephalus. The com-munication was found at the same site, and the

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i 4.

r."be S.

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14

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Fig. 6.-Case 2 Arrow indicates aperture in floor of left ventricle.

corresponding area in the right ventricle was oftranslucent thinness. The cause of the hydro-cephalus here was a fibrillary astrocytoma of thequadrigeminal plate which deformed the iter; inCase 1 a gliosis of the iter was responsible. In theliterature these two types of lesion have often beenconfused, but, though we have insufficient evidenceto deny categorically the neoplastic character ofaqueductal gliosis, there are certain features onwhich we may base a distinction in the present twocases.

1. Macroscopic expansion and deformity of themid-brain.-This was absent in Case 1, but a definitefeature in Case 2.

2. Subdivision and displacement of the aqueduct.In Case 1 subdivision was conspicuous, but theaqueduct occupied its normal position in the mid-line; in Case 2 the aqueduct was displaced anddeformed, but not subdivided.

3. Cytological features of neoplastic growth werenot seen in Case 1. In Case 2 we observed invasionby fibrillary astrocytes of the meninges and Virchow-Robin spaces of blood vessels, also variations in themorphology of the cells with occasional multinu-cleate giant cells.The distinctions indicated in 1 and 2 are probably

of greater value than those in 3.

Case 3. G.H. (R.I. 19190), a female child aged threeyears, was admitted on 3, 11 41, suffering from advancedhydrocephalus which dated from early infancy and wasat first thought to be congenital. There was a story of a

febrile illness at the age of three weeks, and although thedetails were not sufficientlv clear to establish its naturewith certainty, it probably was a meningeal inflammation.The child was brought to hospital because of progres-sive enlargement of the head, and inability to sit orstand. She was a fat, healthy-looking child, with a verylarge head, 61 5 cm. in circumference. Her mentaldevelopment seemed to be normal as judged by speechand behaviour. There was low-grade papillcedema withnormal visual acuity and full fields. There were noabnormalities in the pupils or ocular movements, nor inthe other functions subserved by the cranial nerves. Thelimbs were slightly hypertonic and generally weak, butthere was no definite ataxy. All the tendon reflexes werebrisk, and both plantar responses were extensor. Thereseemed to be no disturbance of sensibility to pin-prickand cotton wool. The spinal fluid pressure was 240 mm.and the fluid contained 60 mgm. protein and 2 cells.X-rays of the skull showed gross separation of the sutures.A ventriculogram revealed a gross dilatation of the wholeventricular system including the 4th ventricle.

Comment.-It was thought that the hydrocephalusresulted from adhesive arachnoiditis which hadoccluded the foramina in the fourth ventricle. Atoperation on the same day an incision was made inthe lamina terminalis by the right frontal approach.The post-operative period was marked by hyper-pyrexia, tachycardia, and other features seen afterventriculography in cases of advanced hydrocephalusand she died on the sixth day.

Pathological ExaminationSummary of Necropsy.-Internal hydrocephalus.

Chronic meningitis. Operation: Ventriculostomy.

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There were no significant changes in chest or

abdomen. The dura was firmly sutured over a

craniotomy opening, 4-5 by 3 cm., in the rightfrontal region. The anterior fontanelle was patent,measuring 12 cm. from side to side and 9 cm. antero-posteriorly. The skull was greatly expanded andtranslucent, the bone being from 0-2 to 0 3 cm. thick.A little muco-pus was present in the left middle ear.

Brain.-Macroscopic.-Both cerebral hemispheres weregreatly and symmetrically expanded and their meningesengorged. There was slight diffuse subarachnoidhemorrhage over the occipital lobes corresponding to the

Fig. 7.-Case 3-Arrow indicates translucent area in floorof right lateral ventricle.

burr-holes made for ventriculography. A patentventriculostomy opening, measuring 0 7 cm. in diameter,occupied the anterior wall of the third ventricle. Therewas grey gelatinous thickening of the leptomeninges overthe whole of the brain stem, forming a pouch with well-defined borders over each foramen of Luschka. In thebasal and interpeduncular cisterns and the proximalparts of the Sylvian fissures a similar thickening wasaccompanied by brownish discoloration. The arachnoidmembrane roofing the cisterna magna was firmly adherentto the dura mater near the mid-line, its margins beingthickened and slightly opaque. This cistern was greatlyexpanded, measuring 3 by 2 by 1 5 cm. in depth, and theforamen of Majendie was so large (I -I by 0-7 cm.) thatthe hind-end of the aqueduct could be viewed through it.The whole of the ventricular system was greatly expanded,the aqueduct measuring 0 7 by 0 5 cm. in cross-section.The right lateral ventricle however was slightly larger thanthe left and the latter was incompletely divided, at the levelof the vestibule, by a falciform septum with a translucent,slightly fenestrated free medial border which extendedfrom the dorsal surface of the choroid plexus to unitewith the roof. This plexus was smooth, grey, andopaque as though embedded in fibrous tissue, and from itextended a thin filament of similar grey tissue uniting withthe medial wall of the ventricle (Fig. 7). A similar filamenttraversed the cavity of the third ventricle parallel withthe anterior and grey commissures. Apart from a finemorocco-leather granularity of the ependyma over thebasal ganglia the walls of the ventricle were smooth, ivorywhite, and corrugated. In the right lateral ventricle thesite of the orifice leading into the leptomeninges observedin Cases I and 2 was occupied by a sharply defined ovaltranslucent membrane, measuring about 1 by 0-6 cm.This was rendered conspicuous in photographing thespecimen by placing a bright light behind it (Fig. 7).

Microscopic.-The translucent area in the hind-part ofthe right ventricle, illustrated in Fig. 7, is formed by amembrane, from 87-5 to 105 pt thick, of fibrillary glia.The ependyma has been lost from its ventricular surfaceand is interrupted over the adjacent hippocampal gyrus.The leptomeninges covering the outer aspect of themembrane are normal apart from a sparse infiltrationwith desquamated arachnoid cells, lymphocytes and afew neutrophil leucocytes.The septum in the left lateral ventricle is composed of

vascularized neuroglial tissue devoid of inflammatoryinfiltration except where it unites with the choroid plexus.The latter is embedded in a richly vascularized layer ofneuroglial and collagenous tissue infiltrated with a fewlymphocytes and small groups of macrophages many ofwhich contain iron pigment. The anterior aspect of thelateral extremity of the septum and adjacent parietal wallof the ventricle are denuded of ependymal cells; a fewshort strips of these cells are present on the posteriorsurface of the septum where it approaches the ventriclewall.The leptomeninges, especially the arachnoid mem-

brane, over the brain stem and cisterna magna arethickened by fibrosis and infiltrated with numerous des-quamated arachnoid cells, many of which have ingestedred corpuscles, while a few contain granules of ironpigment. Free red cells and sparser leucocytes andlymphocytes are also present. The arachnoid membraneover the cisterna magna is united to the dura by fibroustissue and here the arachnoid cells have proliferated toform sheets over the collagenous trabecula. Thefibrosis does not extend however over the lateral lobes ofthe cerebellum, though phagocytic activity of the arach-noid cells is evident and is accompanied by a sparseinfiltration with neutrophil leucocytes. There arenumerous ependymal granulations in the lining of thefourth ventricle.

Summary.-Internal hydrocephalus is due, in thiscase, to chronic leptomeningitis of unknownaetiology. Birth trauma is unlikely to have been thecause since there is little evidence of old haemorrhage;the small amounts of iron pigment present in themeninges over the brain stem, as well as the free andingested red cells, may be attributed to the operationperformed five days before death. It is possiblethat the febrile illness at the age of three weeks was alow-grade meningitis. The observation ofexpansionof the skull from this time onwards is in support ofthis view. There is insufficient evidence to indicatethe origin of the septum and filaments within theventricles.The dilatation of the lateral ventricles was greater

than in Cases 1 and 2, but the concomitant expansionof the skull probably prevented the intra-ventricu-lar pressure from reaching the levels attained whenthe sutures are closed.

General CommentThese cases demonstrate an unusual sequel of

hydrocephalus which may be commoner than wehave realized. Its importance lies chiefly in theinterpretation of ventriculograms-and recogni-tion of its nature should be of guidance in thesurgical treatment of cases such as we have des-cribed.The cystic collection in the leptomeninges was at

first regarded as a diverticulum of the third ventricleuntil necropsy studies showed that it was in com-municatioin with the lateral ventricle. Furtherexamination has shown that it is not a diverticulum

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VENTRICULAR RUPTURE IN HYDROCEPHALUS

of the ventricle, but a collection of cerebro-spinalfluid which escapes into the leptomeninges througha rupture of the wall of the ventricle. The ruptureoccurs in that part of the wall which is thinnestnormally, i.e. in the medial angle of the collateraltrigone (the floor of the ventricle) which lies betweenthe forward-sweeping crus of the fornix, and theforceps major. In this region the ventricular wall isnot supported by any appreciable thickness of whitematter, nor by the basal ganglia, nor by any strongvascular network such as the choroid plexus. Theeffect of ventricular dilatation is to stretch this weakspot by increasing the angle between the crus of thefornix in front and the forceps major behind, and tomake it even more thin. The rupture then takes place,and cerebrospinal fluid escapes beneath the pia. It ispresumably the connection of the pia to the surfaceof the brain which limits the extent of the extra-cerebral collection of fluid to a cyst-like cavity.This enlarges into the most accessible space, i.e. inthe incisura tentorii, and thus insinuates itselfbetween the tentorium above, and the upper surfaceof the cerebellum and brain stem below. As it doesso, it pushes the arachnoid before it, and the cystcan thus be said to be in the subarachnoid space.Passing through the incisura tentorii it occupies theupper part of the cisterna ambiens, and acting as afluid plug it probably adds to the already existingobstruction by embarassing the return of cerebro-spinal fluid from the posterior fossa to the supra-tentorial compartment. In neither of our cases didwe detect any neurological signs which could bereferred to direct pressure of the cyst on neighbour-ing structures.That this process is not a diverticulum of the

ventricle seems to be shown by our third case inwhich the wall of the ventricle was thinned to trans-lucency, but there was no protrusion as would beexpected in the early stages of the development of adiverticulum. The thinning may be bilateral but inour cases the rupture occurred only in one ventricle.Childe and McNaughton (1942) have recentlyreported a case of bilateral loculi of this naturewhich they speak of as ventricular diverticula, butthey recognize the essential feature as being rupture

of the ventricular wall. Sweet (1940) has alsodescribed a similar case discovered at autopsy, andhe suggested the term " ventriculostium."The treatment should be directed to the cause of

the obstruction if that is possible. In cases ofbenign stricture of the aqueduct and neoplasm ofthe brain stem, we may have to be content withprocedures which we hope will short-circuit thecirculation of the cerebrospinal fluid around theobstruction. In many cases, anterior third ventri-culostomy is effective and this is probably theprocedure which should be tried first. If it is noteffective, as in our first case, and subsequent ventri-culograms show that the cyst is large enough to beaccessible by a cerebellar approach, it seems reason-able to attack it from behind. Theoretically,collapse of the cyst should open up the cisternaambiens, and fluid should escape directly from thelateral ventricle into the subarachnoid space withouthaving to traverse the third ventricle. It should besaid, however, that in both of our cases there wasevidence of chronic inflammation in the walls of thecyst which had produced local adhesions in thesubarachnoid space, and it is possible that theseadhesions might limit the efficacy of such an opening.As both of our cases died before they had recoveredfrom the immediate effects of the operation, it isdifficult to assess the value of the procedure, but wefeel that it is worth a further trial.

It is possible that this process affords an explana-tion of some cases of hydrocephalus which seem tobe arrested spontaneously. If the rupture of theventricular wall is accompanied or followed byrupture of the pia, the fluid will escape directly intothe subarachnoid space and we could speak of aspontaneous ventriculostomy. This event would bemore likely in the case of a static or slowly pro-gressive lesion such as benign stricture of theaqueduct than in the case of a neoplastic process.

REFERENCES

Childe, A. E. and McNaughton, F. L. (1942). Arch.Neurol. Psychiat., Chicago, 47, 768.

Sweet, W. H. (1940). Ibid., 44, 532.

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