Book - The Pineal Organ (1940) 27
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The Pineal Organ - The Human Pineal Organ
Chapter 27 Relations of the Adult Pineal Organ
Some of the more important relations are seen in Fig. 276, which is an X-ray photograph of a patient aged 50, showing a calcified pineal, and Fig. 1, p. 2, also of a calcified pineal organ. Fig. 277 is from a section of the pineal region made in the median sagittal plane, and Fig. 278 a transverse section of a brain containing a tumour in the pineal region. Fig. 274
Fig. 275. — Radiographs of Skull, showing Calcification in the Choroid
also shows diagrammatically the position of the great cerebral vein, basal vein, and internal occipital vein to the pineal body ; the relations that a pineal tumour growing backwards beneath the tentorium cerebelli would have to the splenium of the corpus callosum ; the junction of the great cerebral vein with the inferior sagittal sinus to form the straight sinus, and the convolutions and sulci on the adjacent tentorial surface of the brain. The falx cerebri, tentorium, and falx cerebelli, the cerebellum
RELATIONS OF THE ADULT PINEAL ORGAN 413
and pons Varolii are not represented in the diagram. The drawing can thus show the internal occipital vein which lies above and external to the tentorium. Here it issues from the parieto-occipital fissure ; near its termination it crosses the free border of the incisura tentorii and joins the great cerebral vein between the splenium of the corpus callosum above and the pineal body which lies below and internal to it. In this position it would be in direct relation with a pineal tumour. Fig. 279, a transverse and approximately vertical section, gives a notion of the parts in close relationship to the pineal body very different from that obtained from Fig. 278, since it passes through
the posterior part of the fornix and FlG - 276.— Lateral Radiograph of the
Skull of a Patient, aged 50, showing the Typical Appearance of Calcification cf the Pineal Gland.
great cerebral vein, which lie above, the pulvinares of the optic thalami, which are lateral, and the superior colliculi and aqueduct, which lie
below. The close relation of the
cavity of the lateral ventricle, choroid plexus, fimbria, and tela choroidea are also readily appreciated in this section.
The exact position and relations of the pineal body are specially well seen in Fig. 280. It is approximately conical in form, slightly flattened from above downwards, and averages about 8 mm. in length. The base of the gland is directed forwards
and slightly upwards. Its position, which is very constant, is primarily determined by that of the superior or habenular commissure and the
Fig. 277. — Median Sagittal Section of Brain.
THE PINEAL ORGAN
posterior commissure, which lie respectively in its superior and inferior peduncles. The body lies in the groove between the superior colliculi of the quadrigeminal plate, and the apex is directed backwards and slightly downwards. The organ receives a partial covering of pia mater, which is derived from the lower layer of the tela choroidea or velum interpositum. The anterior third or half of its upper surface is covered by the layer of ependyma which forms the floor of the dorsal diverticulum or suprapineal recess. This is continuous with the ependyma lining the
Fig. 278. — Transverse Section of a Brain containing a Tumour of the
cavity of the third ventricle, and is reflected anteriorly over the superior commissure and into the pineal recess. The roof of the superior pineal recess is continuous with that of the third ventricle, and has numerous choroidal villi hanging downwards from it and resting on the upper surface of the pineal body. The posterior two-thirds or half of the upper surface is covered by the lower layer of the tela choroidea which is firmly adherent to its capsule. It is in close relation with the great cerebral vein which separates it from the corpus callosum and commissural fibres of the fornix. The splenium projects backwards beyond the apex of the pineal body. The nerve-fibres of the splenium course outward and
RELATIONS OF THE ADULT PINEAL ORGAN 415
backward over the roof and lateral wall of the posterior horn and hinder part of the inferior horn of the lateral ventricle ; in this situation they form a thin lamina, the " tapetum," inside the fibres of the optic radiation. The latter consist of afferent and efferent fibres which connect the lower visual centres of the lateral geniculate body and superior colliculus with the occipital cortex. It is said that no commissural fibres belonging to
Fig. 279. — Transverse Section of Brain showing Relations of Pineal Body.
Aq. S. : aqueduct of Sylvius.
C.C. : corpus callosum.
Ch. P. : choroid plexus.
C.N. III. : third cranial nerve.
F. : fornix, beneath which is the great transverse fissure.
H.M. : hippocampus major.
I.C. : internal capsule.
I.C.L.V. : inferior horn of lateral ventricles.
L.G.B. : lateral geniculate body.
L.V. : lateral ventricle.
the visual area of the cortex cross in the corpus callosum. So far as we are aware, little is known about the function of the fibres of the tapetum and the fibres of the forceps major which cross in the splenium of the corpus callosum, and injury to these fibres does not appear to give rise to any definite symptoms or disability.
The under surface of the pineal body is typically separated from the groove between the superior colliculi by a fold of pia mater, which forms
M.G.B. : medial geniculate body.
N.P. : nuclei pontis.
O.M.N. : oculo-motor nucleus and
medial longitudinal fascicle. Op. T. : optic thalamus. R.N. : red nucleus. S.C. : superior colliculus. S.C.P. : superior cerebellar peduncle
(brachium conjunctivum). S.N. : substantia nigra. V.M.C. : vena magna cerebralis.
416 THE PINEAL ORGAN
a recess called the subpineal cul de sac of Reichert. This may reach forward as far as the posterior commissure or it may become obliterated by adhesions. The lateral surfaces are also covered with pia mater which
Fig. 280. — Drawing of a Medial Longitudinal Section through the Pineal Region of a Human Subject showing the Relations of the Pineal Organ to the Corpus Callosum, Fornix, Great Cerebral Vein, Dorsal Diverticulum, and Choroid Plexus, Superior and Posterior Commissures, Quadrigeminal Plate, and the Membranes and Blood-vessels at its Posterior Pole. (R. J. G.)
Aq. C. : aqueductus cerebri.
Cbl. : cerebellum.
C.C. : corpus callosum.
Ch. P. : choroid plexus.
D.D. (S.P.R.) : dorsal diverticulum
(superior pineal recess). Ep. : ependyma. F. : fornix P.B. : pineal body.
P.C. : posterior commissure.
O.T. : optic thalamus.
R.P. : recessus pinealis.
S.C. : superior commissure.
Spl. : splenium.
5. Col. : superior colliculus.
Teg. : tegmentum.
V .CM. : gr. vein of Galen.
V. III. : third ventricle. may be continued backward from the sides and apex of the organ as a fold which contains between its layers vessels, nerves, and the ganglion conari (Kolmer, Lowy, and Pastori). The nerve-fibres are described as being of two kinds — " fine," which are the more numerous, and " coarse,"
RELATIONS OF THE ADULT PINEAL ORGAN 417
both sets of fibres belong to the sympathetic system. This fold has been described as the posterior ligament (Calvet), whereas the reflections at the side are styled the lateral ligaments. In some cases the body and apex of the pineal organ are completely surrounded by a plexus of vessels lying in the subpial tissue and containing calcareous concretions. In old subjects this tissue is often very dense and thick, so that considerable difficulty may be experienced in freeing the body from its surroundings.
At the base of the organ are the superior and inferior peduncles and an intermediate or lateral peduncle (Calvet) which connects the pineal body with the medial surface of the thalamus. The superior peduncle contains medullated nerve-fibres belonging to the superior or habenular commissure, and the inferior peduncle conveys similar fibres of the posterior commissure ; between the two commissures is the pineal recess.
The superior peduncle is continued forward on each side as the habenula (Fig. 281). This forms the inner boundary of the trigonum habenulae, and anteriorly is continuous with the taenia thalami, which marks the lateral limit of the roof of the third ventricle and the line along which the ependyma on the lateral wall of the ventricle leaves the medial surface of the thalamus. The habenular ganglion is situated in relation with the posterior and median part of the optic thalamus, beneath the trigonum habenulae. It receives afferent fibres from the stria medullaris thalami, which if traced backwards divide into two bundles, of which one joins the ganglion of the same side while the other crosses in the habenular commissure to the ganglion of the opposite side. The stria medullaris is connected in front with the anterior pillar of the fornix, these fibres being derived from the cells in the hippocampal cortex, whereas a ventral bundle of fibres comes from a collection of cells in the anterior perforated substance. It is believed, therefore, that in the human subject the habenular commissure is chiefly composed of decussating fibres belonging to the olfactory system and that each habenular ganglion receives relays of fibres from the olfactory organ of both the right and left side. In lower vertebrates, however, such as the cyclostomes, in which definite pineal sense-organs are present, the habenular ganglia receive afferent fibres which arise in the ganglion cells of the retinae of the pineal eyes, and in the human subject some of the fibres of the habenular commissure appear to terminate in the basal part of the pineal body (see p. 408).
The posterior commissure : in spite of the position of the posterior commissure, as seen in median longitudinal sections of the brain, being so familiar and such a valuable landmark, it has been found difficult to trace its connections with certainty, and there is considerable difference of opinion with regard to the origin of its fibres. Most authors are, 27
418 THE PINEAL ORGAN
however, agreed that in the human subject some of its fibres arise in the nucleus interstitialis or nucleus of origin of the median longitudinal
N.C fCh.Pi 1
F. 1 V.M.C!
S. — V.M.C. 2
Fig. 281. — Pineal Region Viewed from Above. The upper part of the right hemisphere of the brain has been removed and the right lateral ventricle opened by removal of portions of the corpus callosum and the roof of the posterior and inferior cornua. A part of the fornix and tela choroidea were then cut away so as to expose the pineal body, habenular region, and superior colliculus. The pineal body of the adult lies between 5 and 6 cm. directly below the supero-medial border of the hemisphere, and its apex is 1 cm. in front of the posterior end of the splenium of the corpus callosum. The great cerebral vein lies in the velum interpositum (T. Ch.) between the pineal body below and the fornix and corpus callosum above. C. : cerebellum. O. Th. : optic thalamus.
Ch. PI 1 and 2 : choroid plexus. P.B. : pineal body.
C.S. : colliculus superior. 5. : splenium of corpus callosum.
F. 1 and 2 : fornix. V.B. : vena basilaris.
N.C. : nucleus caudatus. V.M.C. 1 and - : vena magna cerebralis.
(Original : R. J. G.)
fasciculus, and that the decussating fibres have connections through this tract with the nuclei and nerve-fibres of the eye muscles. The com
RELATIONS OF THE ADULT PINEAL ORGAN 419
missure also appears to contain fibres which originate or end in nuclei situated in the tectum opticum.
In cyclostomes, e.g. Petromyzon, in addition to fibres which are associated with the pineal system, fibres of the posterior commissure arise from cells which are widely scattered through the dorso-caudal part of the thalamus and tectum opticum. In Geotria, the Australian lamprey, according to Dendy the larger of the two organs, the right parietal organ (Epiphysis II or posterior pineal organ) is connected by a well-defined tract, the pineal nerve with the right habenular ganglion, and also sends fibres to the posterior commissure and right bundle of Meynert ; whereas the smaller deeply placed left parietal organ (Epiphysis I or parapineal organ of Studnicka) is joined by a few short fibres with the left habenular ganglion which lies immediately beneath it, and also sends fibres to the posterior commissure and the left bundle of Meynert. The morphology of the pineal tract and of the habenular commissure in cyclostomes is discussed on p. 193. Briefly summarized it may be stated that two organs or pairs of organs have been considered by some authors to be comprised in the pineal system, of which the anterior organ or Epiphysis I is related to the habenular ganglia and the habenular commissure, and the posterior organ or Epiphysis II is connected with the posterior commissure. It is this Epyphysis II in a modified form which is said to be represented by the epiphysis of amphibia ; the pineal sac or epiphysis of reptiles ; and the epiphysis of birds and mammals.
Having considered the immediate relations of the pineal body and the principal connections of the habenular and posterior commissures, it will be advantageous to examine the structures which lie around the pineal zone, and which are liable to be compressed by a tumour originating in these regions, or would have to be borne in mind when approaching the organ with the object of removing a tumour. A glance at the transverse section (Fig. 279) will show the relations of the tela choroidea with its contained vessels to the transverse fibres and fimbria; of the fornix and also the connection of the latter with the body of the corpus callosum. Overlapping the fimbria of the fornix on each side is the choroid plexus, which projects into the lateral ventricle. The size, vascularity, and density of the plexus varies considerably in different individuals. In the specimen drawn the lateral ventricle is of moderate size, but in cases of obstruction to the aqueduct of Sylvius the ventricle may be greatly distended or, if emptied, the walls may be collapsed. On either side of the pineal body is the pulvinar of the optic thalamus. This is separated from the pineal body, superior colliculus, and superior brachium by pia mater containing blood-vessels. Lateral to the pulvinar is the internal capsule, passing between the caudate and lenticular nuclei and coursing down
420 THE PINEAL ORGAN
ward into the crura cerebri. Immediately beneath the pineal body is the roof of the aqueduct, containing the tecto-spinal and tecto-bulbar nuclei. Around the aqueduct is the central grey matter and below it the various nuclei of the third nerve, the nuclei of the fourth nerve, and the medial longitudinal fasciculi (Fig. 279, p. 415), which if traced downwards are found to be connected on each side with the superior olive, the nucleus of the sixth cranial nerve, and that of the vestibular nerve. Ventral to the nuclei of the third nerve are the red nuclei, the decussation of the rubro-spinal tract, and the substantia nigra ; while dorso-lateral to the red nucleus is the medial lemniscus. Ventral to the red nuclei is the substantia nigra and near the outer borders of this are seen the medial geniculate bodies. Passing upwards round the outer side of the crus cerebri are the posterior cerebral and superior cerebellar arteries, with the fourth nerve running ventrally and forwards between them. The basal vein also, as mentioned previously, occupies the recess between the crus cerebri and medial geniculate body on the inner side, and the tail of the caudate nucleus, inferior horn of the lateral ventricle, choroidal fissure, fimbria, and hippocampus are on the outer side. Finally the apex of the pineal body is seen in a medial section (Fig. 280) to be in close relation to the superior vermis of the cerebellum, and if the organ is enlarged it may exert direct pressure on this and the superior peduncles or brachia conjunctivae. Should a tumour of the pineal body enlarge forward into the third ventricle it may exert pressure on the interpeduncular and subthalamic regions and upon the optic thalami laterally.