Journal of Clinical Neuroscience 19 (2012) 289-298
Contents lists available at SciVerse ScienceDirect
Journal of Clinical Neuroscience
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j o c n
Neuroanatomical Study
Analysis of the anatomy of the Papez circuit and adjoining limbic system
by fiber dissection techniques
Abhidha Shah, Sukhdeep Singh Jhawar, Atul Goel
Department of Neurosurgery, Seth G.S Medical College and King Edward VII Memorial Hospital, Acharya Donde Marg, Parel, Mumbai 400012, India
a r t i c l e
i n f o
a b s t r a c t
Article history:
Fiber dissection techniques were used to study the limbic system, in particular the Papez circuit. The
Received 23 February 2011
course, length and anatomical relations of the structures that make up the Papez circuit were delineated.
Accepted 23 April 2011
Ten previously frozen and formalin-fixed cadaveric human brains were used, and dissected according to
the fiber dissection techniques of Klingler et al. (Schweiz Arch Neurol Psychiatry 1935;36:247-56). The pri-
mary dissection tools were thin and curved wooden and metallic spatulas with tips of varying sizes. We
Keywords:
found that the Papez circuit (mean length: 350 mm) begins in the hippocampus and continues into the
Fiber dissection
fornix to reach the mamillary body. From there, the mamillothalamic tract continues to the anterior
Limbic connections
nucleus of the thalamus, which in turn connects to the cingulum by means of anterior thalamic radiations
Limbic system
Papez circuit
(mean length: 30 mm). The cingulum courses around the corpus callosum to end in the entorhinal cortex,
which then projects to the hippocampus, thus completing the circuit. The average length and breadth of
the mamillothalamic tract was 18 mm and 1.73 mm respectively. The average length of the cingulum was
19.6 cm and that of the fornix was 71 mm. The entire circuit was anatomically dissected first in situ in the
hemisphere and was then reconstructed outside after removing its various components using fine fiber
dissection under a surgical microscope. We found that fiber dissection elegantly delineates the anatom-
ical subtleties of the Papez circuit and provides a three-dimensional perspective of the limbic system.
Intricate knowledge of the anatomy of this part of the brain aids the neurosurgeon while performing epi-
lepsy surgery and while approaching intrinsic brain parenchymal, ventricular and paraventricular lesions.
O 2011 Elsevier Ltd. All rights reserved.
1. Introduction
been used to their potential in evaluating and studying the micro-
neurosurgical anatomy of this region.
The limbic system is among the most complex and least under-
stood parts of the nervous system. The term ``limbus'' means ``bor-
2. Materials and methods
der'' or ``margin'' in Latin. This region of the brain was first pictured
by Thomas Willis and he referred to it as ``the limbus'' as early as
2.1. Preparation
1664.1 In 1878, Paul Broca referred to it as ``le grande lobe lim-
bique'' and described it as a cortical ring surrounding the hilus of
The preparation of cadaveric brain specimens and dissection
the hemispheres.2 James Papez postulated that the anatomical ba-
techniques were based on Klingler et al.6 Ten normal human cere-
sis of emotions was found in the hypothalamus, anterior thalamic
bral hemispheres were fixed in 10% formalin for 30 days. They
nuclei, cingulate gyrus, hippocampus and in their interconnec-
were then frozen at A10 C for three weeks to four weeks. The
tions.3 MacLean, in 1949, termed these cortical and subcortical sys-
hemispheres were then allowed to thaw under water for
tems and their fiber connections as ``the limbic system''.4 Using
24 hours.7,8
silver degeneration techniques, Nauta extended the limits of the
limbic system to include the midbrain.5
2.2. Tools
We have used the fiber dissection technique to depict the
various components of the limbic system, in particular the Papez
The dissection was done with the aid of the operating microscope
circuit. To our knowledge, fiber dissection techniques have not
(6-40A magnification). The hemispheres were stored in 4% formalin
between the dissection sessions. Our primary dissection tools were
hand-made wooden spatulas with different sized spatula tips for
superficial and deep dissection. The dissection was commenced
Corresponding author. Tel.: +91 22 24129884; fax: +91 22 24143435.
from the medial surface of the cerebrum. Photographs were taken
E-mail address: atulgoel62@hotmail.com (A. Goel).
at each step of the dissection to demonstrate the anatomy.
0967-5868/$ - see front matter O 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jocn.2011.04.039

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2.3. Medial to lateral dissection of the white matter
21.3 mm (20-23 mm) and an average breadth of 2.3 mm (2-
2.6 mm). The average distance between the mamillothalamic tract
For anatomical delineation of the Papez circuit and the limbic
and the fornix was 6.4 mm (6-7 mm). To complete the circuit, the
system, a medial cerebral hemispheric approach was used
continuation of the mamillothalamic tract was traced to the cingu-
(Fig. 1). The cerebral hemispheres were bisected in the midline
lum. The corpus callosum was removed carefully, avoiding damage
through the corpus callosum. The medial and lateral longitudinal
to the cingulum (Fig. 6). The caudate head and body in the floor of
striae were identified on the surface of the corpus callosum before
the lateral ventricle were visualized. The stria terminalis was seen
splitting the brain (Fig. 2). Major anatomical landmarks on the
running between the thalamus and the caudate nucleus. The epen-
medial surface of the cerebral hemisphere were identified
dyma over the caudate head was removed. The whole caudate
(Fig. 1). The ependymal coverings over the medial surface of the
head was then lifted off in one piece to reveal the underlying ante-
thalamus and the hypothalamus were peeled off carefully. The dis-
rior thalamic fibers radiating from the anterior nucleus of the thal-
section was then begun with coring off of the gray matter of the
amus and entering into the undersurface of the cingulum (Figs 7
thalamus (Fig. 3). The mamillothalamic tract was identified run-
and 8). The average length of the anterior thalamic radiations from
ning upward from the mamillary body. The average length of the
the anterior nucleus of the thalamus to the point where they en-
mamillothalamic tract was 18 mm (17.4-18.2 mm) and its breadth
tered the cingulum was 3 cm. These fibers intermingled with the
was 1.73 (1.6-1.8 mm). The tract was traced carefully till it was
fibers of the anterior limb of the internal capsule and transverse fi-
seen entering the anterior nucleus of the thalamus. The mamillo-
bers of the corpus callosum. This completed the dissection and iso-
tegmental tract was identified emerging from the mamillary body
lation of the Papez circuit, which begins at the hippocampus,
and going up to the midbrain tegmental nuclei ventral to the aque-
continues as the fimbria and fornix and terminates into the mam-
duct. Subsequent to this the gray matter of the cingulate gyrus
illary body. From the mamillary body the mamillothalamic tract
above the corpus callosum was cored out and the cingulum was
then reaches the cingulum, which turns around the splenium of
identified, and traced anteriorly till its culmination in the subcallo-
the corpus callosum to end as the radiation of the cingulum into
sal area and the paraterminal gyrus. Posteriorly, the cingulum nar-
the hippocampus, thus completing the loop.
rowed above the splenium into the isthmus of the cingulum and
Further dissection was then continued in the basal forebrain re-
then continued into the medial temporal lobe to end as the radia-
gion. The olfactory tract was identified and observed splitting into
tion of the cingulum which could be identified after removal of the
the medial and lateral olfactory striae (Fig. 9). The medial olfactory
parahippocampal gray matter. After tracing the whole length of the
stria was traced and was seen to end in the subcallosal gyrus. The
cingulum, the fibres of the cingulum entering into the frontal and
lateral olfactory stria ended in the piriform cortex and the amyg-
parietal cortices were traced. The average length of the cingulum
dala. The anterior perforated substance was identified between
was 19.6 cm (19-20.4 cm).
the medial and lateral olfactory striae. Deeper dissection was then
Attention was now turned to the mesial temporal brain. The
performed to trace the anterior commissure. The anterior commis-
gray matter of the parahippocampal gyrus was removed to visual-
sure was identified anterior to the column of fornix. The entire
ize the subiculum, dentate gyrus and fimbria of the fornix (Fig. 4).
length of the anterior commissure was traced in both the hemi-
The gray matter was traced posteriorly and superiorly till it contin-
spheres (Fig. 10). The average length of the anterior commissure
ued into the crus of the fornix. The body of the fornix was sepa-
on one side was 39 mm (37-40 mm) and the total length was
rated from the under-surface of the corpus callosum by blunt
78 mm (74-80 mm). The mean breadth of the anterior commissure
dissection. The body of the fornix was then traced anteriorly into
was 3 mm (3-3.3 mm). The various components of the limbic sys-
the columns of the fornix, which ended in the mamillary body
tem were then removed using fine dissection and a reconstructed
(Fig. 5). The columns of the fornix had an average length of
model was made (Fig. 11).
Fig. 1. Photograph of the medial view of the cerebral hemisphere showing the various anatomical landmarks: a, corpus callosum; b, frontal horn of lateral ventricle; c, choroid
plexus in the choroidal fissure; d, choroidal fissure; e, thalamus; f, fornix; g, anterior commissure. (This figure is available in colour at www.sciencedirect.com.)

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291
Fig. 2. Photograph of the superior view of the corpus callosum: a, corpus callosum; b, indusium griseum; c, longitudinal striae; d, cingulate gyrus running above the corpus
callosum. (This figure is available in colour at www.sciencedirect.com.)
Fig. 3. Photograph of the dissection of the medial aspect of the hemisphere: a, paraterminal gyrus; b, subcallosal gyrus; c, corpus callosum; d, caudate head in frontal horn of
lateral ventricle; e, anterior commissure; f, body of fornix; g, columns of fornix; h, mamillary body; i, mamillothalamic tract; j, mamillotegmental tract; k, uncus; l,
parahippocampal gyrus; m, parahippocampal gyrus continuing as cingulate gyrus superiorly; and as n, lingual gyrus inferiorly. (This figure is available in colour at
www.sciencedirect.com.)
3. Results and discussion
fasciculus and the medial forebrain bundle.9,10A brief description
of the key components of the limbic system is given below.
The limbic system is phylogenetically one of the more primitive
parts of the brain and is composed of both gray and white matter.
3.1. Parahippocampus
The gray matter component of the limbic system is composed of
the hippocampal formation, amygdaloid nuclei, hypothalamus, nu-
The parahippocampal gyrus lies at the junction of the medial
cleus accumbens, cingulate cortex, areas of the prefrontal cortex,
and inferior portions of the temporal lobe. Anteriorly and medially
and nuclei of the midbrain. The fiber bundle components of the lim-
it curves to form the uncus. Laterally and anteriorly the parahippo-
bic system include the cingulum, longitudinal striae, fornix, ante-
campal gyrus is limited by the rhinal sulcus, which marks the lat-
rior commissure, mamillothalamic and mamillotegmental tracts,
eral extent of the entorhinal area of the parahippocampal gyrus.
stria terminalis, striae medullaris thalami, diagonal band of
The entorhinal area has many afferent and efferent connections
Broca, fasciolus retroflexus, ansa peduncularis, dorsal longitudinal
with the hippocampus and the association areas of the cortex

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Fig. 4. Photograph of the dissection of the mesial temporal structures: a, hippocampus; b, radiation of the cingulum; c, dentate gyrus; d, fimbria; e, fasciolar/subsplenial
gyrus. (This figure is available in colour at www.sciencedirect.com.)
Fig. 5. Photograph showing the mamillary body and surrounding structures after the removal of the dentate gyrus: a, hippocampus; b, fimbria; c, crus of the fornix; d, body of
the fornix; e, column of the fornix; f, mamillary body; g, mamillothalamic tract; h, anterior nucleus of the thalamus. (This figure is available in colour at
www.sciencedirect.com.)
and forms an important relay center. Posteriorly, the parahippo-
The parahippocampal gyrus extends from the inferior surface
campal gyrus is divided by the anterior calcarine sulcus into the
medially towards the hippocampal fissure where it curves inwards
isthmus of the cingulate gyrus superiorly which continues as the
to form the hippocampus, which in turn again curves inwards to
cingulate gyrus and the parahippocampal gyrus inferiorly which
form the dentate gyrus. The portion of the parahippocampal gyrus
continues as the lingual gyrus11 (Fig. 3).
at the edge of the hippocampal fissure is known as the subiculum

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293
Fig. 6. Photograph of the cingulum and surrounding structures after the anterior half of the corpus callosum had been cut and removed: a, cingulum; b, fibers of the cingulum
entering into the parietal cortex; c, corpus callosum; d, head of caudate nucleus; e, body of the fornix; f, columns of the fornix; g, mamillary body; h, mamillothalamic tract; i,
anterior nucleus of the thalamus; j, radiation of the cingulum; k, paraolfactory gyrus; l, paraterminal gyrus. (This figure is available in colour at www.sciencedirect.com.)
Fig. 7. Photograph of the anterior thalamic radiation after the caudate head had been lifted off in one piece: a, caudate head; b, anterior thalamic radiation; c, fornix; d,
mamillary body; e, mamillothalamic tract. (This figure is available in colour at www.sciencedirect.com.)
and the area between the subiculum and the parahippocampal
meaning ``support'') which forms the superior surface of the
gyrus is known as the presubiculum.9
parahippocampal gyrus. The hippocampus is separated from the
parahippocampal gyrus and the subiculum by the hippocampal fis-
3.2. Hippocampus
sure. Embryologically, the hippocampal formation is laid down
along the hippocampal fissure. This fissure lies above and parallel
The hippocampus (Greek meaning ``seahorse'') is where the
to the choroidal fissure. As the temporal lobe develops, both these
Papez circuit begins and ends. It rests on the subiculum (Latin
fissures are carried downwards and forwards to form a C-shaped

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Fig. 8. Photograph of the anterior thalamic radiation projecting to the cingulum after the caudate head had been removed in one piece. Fibers forming the cingulum can also
be seen radiating to the frontal cortex: a, anterior thalamic radiation; b, cingulum; c, fibers from the cingulum entering the frontal cortex; d, cut end of the corpus callosum; e,
body of fornix; f, crus of fornix; g, anterior commisure; h, mamillary body; i, mamillothalamic tract; j, anterior nucleus of thalamus. (This figure is available in colour at
www.sciencedirect.com.)
Fig. 9. Photograph of the inferior surface of the brain showing the basal forebrain region: a, olfactory tract; b, lateral olfactory stria; c, medial olfactory stria; d, anterior
perforated substance; e, anterior commissure; f, gyrus rectus. (This figure is available in colour at www.sciencedirect.com.)
configuration.9 The hippocampal formation does not develop to the
gyrus and the subiculum. The hippocampal formation forms the
same extent across the whole length of the hippocampal fissure.
medial part of the floor of the temporal horn. From the hippocam-
The dorsal part of the fissure is invaded by fibers of the corpus cal-
pus, fibers form a band known as the alveus (Latin meaning trough
losum and the hippocampal formation in this portion becomes a
or hollow) that is located on its dome. It continues as the fimbria.
vestigeal band - the indusium griseum.9,12 The inferior portion of
Lateral to the fimbria and separated from it by the fimbrio-dentate
the hippocampal fissure differentiates into the hippocampal for-
sulcus, lies the dentate gyrus. When viewed from the medial as-
mation which consists of the hippocampus proper, the dentate
pect, the dentate gyrus is visualized as a thin band of cortex with

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295
Fig. 10. Photograph showing the inferior surface of the basal forebrain after deeper dissection: a, anterior commissure; b, anterior portion of anterior commissure; c, posterior
portion of anterior commissure; d, diagonal band of Broca. (This figure is available in colour at www.sciencedirect.com.)
Fig. 11. Photograph of a reconstructed model showing the various connections of the limbic system. (This figure is available in colour at www.sciencedirect.com.)
a toothed appearance that lies between the fimbria above and the
3.3. Fornix
hippocampal fissure below (Fig. 4). The fimbria and the dentate
gyrus run together posteriory till the splenium. Here, the dentate
The fornix constitutes the main efferent pathway from the hip-
gyrus loses its denticulations and becomes the fasciolar gyrus
pocampus, though it also carries a few afferent fibers. The fornix is
which then runs superiorly over the corpus callosum. On the supe-
composed of axons from the subiculum and the pyramidal cells of
rior surface of the corpus callosum, the fasciolar gyrus becomes a
the hippocampus. The fornix begins as the alveus and the fimbria.
thin lamina of gray matter, namely the indusium griseum, also
The fimbria then forms the crus of the fornix (Latin meaning ``vault
known as the supracallosal gyrus.9,12 Running within the indusium
or arch'') which curve superolaterally over the pulvinar of the thal-
griseum are two bands of myelinated fibers, the medial and lateral
amus (Figs 4 and 5). Further anteriorly, the two crura meet in the
longitudinal striae of Lancisii (Fig. 2). The indusium griseum and
midline to form the body of the fornix. The two crura of the forn-
the longitudinal striae course over the entire corpus callosum
ices are connected by the hippocampal commissure or psalterium.
and terminate in the paraterminal gyrus. The paraterminal gyrus
Information is transmitted from one hemisphere to the other
then continues as the diagonal band of Broca.
through this pathway. The body of the fornix runs forward to the

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anterior end of the thalamus, where the fibers of the two sides
widespread connections to the rest of the limbic system and there-
again separate and arch downwards in front of the intraventricular
fore provides an important route by which the amygdala can affect
foramen as the columns of the fornix. The fibers of the fornix on
structures beyond the connections of the stria terminalis itself. The
approaching the anterior commisure divide into a pre commissural
ventral amygdalofugal pathway courses medially from the amyg-
and a post commissural portion. Most of the fibers form the post
dala to the basal nucleus of Meynert and the dorsal medial nucleus
commissural portion.9,13 These fibers arise mainly from the subic-
of the thalamus. It is a diffuse, myelinated bundle lying ventral to
ulum and terminate into the mammillary body. These fibers reach
the globus pallidus (medial pole). It courses medially and rostrally
the mammillary body and en route also give fibers to the lateral
beneath the lentiform nucleus, passes through the substantia
and anterior nucleus of the thalamus and to the lateral septal nu-
innominata to reach the hypothalamus, septal areas, lateral preop-
clei. Thus, the anterior nucleus of the thalamus receives fibers form
tic area and the nucleus of the diagonal band of Broca. Some fibers
the mamillothalamic tract and also recieves direct fibers from the
proceed via the inferior thalamic peduncle to reach the dorsomedi-
post-commissural fornix. A few fibers pass ventral to the anterior
al nucleus of the thalamus.9
commissure as the pre-commissural fornix. These fibers essentially
originate mainly from the pyramidal cells of the hippocampus.
3.7. Basal forebrain
Their input is principally to the septal nuclei, the lateral pre-optic
area, the anterior part of the hypothalamus and the nucleus of the
The
mediobasal
frontal
cortical
area
of
each
cerebral
diagonal band.9 The pre-commisural fibers form a small compact
hemisphere, composed of the paraterminal gyrus and the paraol-
bundle that cannot be detected grossly. The post commissural for-
factory gyri, is also considered a limbic cortical area.12 It extends
nix terminates into the medial mammillary nucleus. Fibers then
from the olfactory tubercle rostrally to the hypothalamus caudally.
arise from here and ascend upwards to the anterior nucleus of
It lies over the anterior perforated substance and does not have any
the thalamus forming the mamillothalamic tract of Vicq d'Azyr.
definite boundaries. The basal forebrain includes the septal area,
Near its origin, the mamillothalamic tract gives rise to another
the olfactory tubercle, parts of the amygdala and the substantia
smaller bundle known as the mamillotegmental tract (Fig. 3)
innominata (basal nucleus). The lateral olfactory stria and gyrus
which terminates according to many authors into the tegmental
pass along the lateral margin of the anterior perforated substance
nucleus of Gudden.5,14,15 From the anterior nucleus of the thalamus
to reach the piriform region. These fibers terminate in the piriform
fibers radiate upward and mingle with the fibers of the anterior
cortex and in the corticomedial part of the amygdaloid nuclear
limb of the internal capsule to reach the cingulum (Latin meaning
complex.
``girdle'') and the cingulate gyrus (Figs 7 and 8).
The medial olfactory stria becomes continuous with the subcal-
losal and the paraterminal gyrus (Figs 9 and 10). The subcallosal
3.4. Cingulum
area and the paraterminal gyrus constitute the septal area, beneath
which are the septal nuclei. The septal region is situated on the
The cingulum is an association bundle which runs superior and
medial surface of the cerebral hemisphere, immediately facing
parallel to the corpus callosum. Its fibers terminate anteriorly be-
the anterior commissure. The medial septal nucleus becomes
low the rostrum of the corpus callosum in the subcallosal gyrus.
continuous with the nucleus and tract of the diagonal band of
Posteriorly the cingulum narrows above the splenium, where it
Broca, which then connects with the hippocampal formation. The
forms the isthumus of the cingulum and this continues below as
septal nuclei receive afferents principally from the hippocampus
the radiation of the cingulum to end in the anterior parahippocam-
and subiculum of the parahippocampal gyrus via the indusium
pal region adjacent to the hippocampus (Fig. 6).
griseum as well as from the precommissural fornix. The efferents
of the septal nuclei project to the area surrounding the hippocam-
3.5. Dentate gyrus
pus via the fornix itself, to the hypothalamus and midbrain tege-
mentum via the medial forebrain bundle, to the habenula via the
The dentate gyrus (Fig. 4) receives input mainly from the
stria medullaris thalami, which in turn projects to the mesenceph-
entorhinal area. The input is mainly by means of two pathways,
alon via the fasciolus retroflexus.9,12 Functionally, the septal nuclei
the perforant path and the alvear path. The fibers of the perforant
are responsible for connecting limbic structures with the hypothal-
path originate in the lateral part of the entorhinal cortex, traverse
amus and the brainstem, principally via the hippocampal
through the subiculum and terminate in the dentate gyrus. The
formation.
alvear path originates in the medial part of the entorhinal cortex
and enters the hippocampus from the ventricular surface after tra-
3.8. Anterior commisure (Figs 10 and 12)
versing the alveus.9
The anterior commissure crosses the midline anterior to the
3.6. Amygdala
columns of the fornix. The entire extent of the anterior commissure
resembles a horizontally placed bow. It runs in a canal of gray
The amygdala (Greek meaning ``almond-like'') lies entirely with-
matter (canal of Gratiolet) parallel and deep to the uncinate
in the confines of the uncus. The amygdala gives rise to two major
fasciculus and the occipitofrontal fasciculus. The average distance
pathways, the stria terminalis and the ventral amygdalofugal path-
of the anterior commissure from the temporal pole was 18 mm
way.9 The stria terminalis is a C-shaped structure which exits from
(16-20 mm) and the average distance of the uncinate fasciculus
the ventromedial portion of the amygdala and arches along the en-
from the anterior commissure was 6 mm (3-8 mm) Laterally the
tire medial border of the caudate nucleus near its junction with the
anterior commissure splits into two, an anterior or olfactory
thalamus, around the lateral ventricle. These fibers terminate in
portion and a posterior or temporal portion (Fig. 12). The anterior
the bed nuclei of the stria terminalis which lies lateral to the col-
portion of the commissure consists of fibers arising from the
umns of the fornix and dorsal to the anterior commissure. Some fi-
anterior olfactory nucleus, which cross to the opposite side and
bers also terminate in the hypothalamus and some join the medial
end in the anterior olfactory nucleus on the contralateral side.
forebrain bundle.9
The posterior or the temporal portion of the anterior commissure
The bed nucleus of the stria terminalis, runs along with the stria
forms the major bulk and passes laterally, deep to the lentiform
terminalis and is largest rostrally. It receives input from all nuclei
nucleus, to end in the middle temporal gyrus. Some fibers enter
of the amygdala. The bed nucleus of the stria terminalis has
the external capsule laterally and some fibers course posteriorly

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297
Fig. 12. Photograph showing the lateral view of the cerebral hemisphere. The insular region has been dissected to show the course of the posterior portion of the anterior
commissure: a, anterior commissure; b, limen insulae; c, internal capsule; d, sagittal stratum and optic radiations. (This figure is available in colour at
www.sciencedirect.com.)
as part of the sagittal stratum (Fig. 12). The anterior commissure
hippocampus, cingulum and fornix in patients with mesial tempo-
has a role in the transfer of visual, olfactory and auditory informa-
ral lobe epilepsy.18 DTI studies have reported decreased fractional
tion between the temporal lobes.
anisotropy of the cingulum bundle in patients suffering from
schizophrenia and Alzheimer's disease.18 Thus the study of the
3.9. Limbic connections between the telencephalon, diencephalon and
structure of the Papez circuit by DTI can be used as a diagnostic
mesencephalon
and monitoring tool in patients with neurological disorders.
Limbic systems are affected in lesions of the medial and basal
The stria medullaris is a fiber bundle that runs from the septal
surfaces of the cerebral hemispheres and the diencephalon. Some
region to the habenular nuclei. The impulses from the habenular
of the fiber systems are traversed in approaching lesions of the
nuclei are then conveyed via the fasciculus retroflexus to the
lateral and third ventricle. Lesions originating from the medial
midbrain.16
frontal, parietal and occipital lobes, from parts of the cingulate
The medial forebrain bundle projects to the midbrain tegmen-
gyrus, corpus callosal lesions and lateral ventricular tumors can
tum, after originating from the septal and lateral preoptic region.
be approached via a transcortical and an interhemispheric ap-
It also carries ascending fibers from the midbrain. Ascending fibers
proach. The merits and deficiencies of both the approaches have
to the mamillary body run in the mamillary peduncle. They arise
been discussed extensively. Along with injuries to cortical areas,
from the dorsal and ventral nuclei of Gudden and traverse to the
trans-cortical approaches disrupt the white matter tracts in the
mamillary body. Some fibers continue rostrally to the lateral
region. The white matter tracts at risk are the cingulum and the
hypothalamic regions, medial septal nuclei and preoptic areas via
connections between the cingulum and the frontal, parietal and
the medial forebrain bundle.16
occipital cortices. The anatomy of the hippocampus, amygdala
and its relations are important to know while performing epilepsy
surgery. A transforaminal transchoroidal approach to the third
4. Clinical Implications
ventricle avoids damage to the fornix. A thorough knowledge of
the anatomy and physiology of the limbic system can aid the
Diffusion tensor imaging (DTI) and diffusion spectrum imaging
neurosurgeon while approaching and operating in this region.
(DSI) have been used to study the components of the Papez circuit
non-invasively.17,18 Granziera et al. used DSI and showed the three
major fiber bundles of the Papez circuit and some sparse connec-
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Document Outline

• Analysis of the anatomy of the Papez circuit and adjoining limbic system by fiber dissection techniques
  • 1 Introduction
  • 2 Materials and methods
    • 2.1 Preparation
    • 2.2 Tools
    • 2.3 Medial to lateral dissection of the white matter
  • 3 Results and discussion
    • 3.1 Parahippocampus
    • 3.2 Hippocampus
    • 3.3 Fornix
    • 3.4 Cingulum
    • 3.5 Dentate gyrus
    • 3.6 Amygdala
    • 3.7 Basal forebrain
    • 3.8 Anterior commisure (Figs 10 and 12)
    • 3.9 Limbic connections between the telencephalon, diencephalon and mesencephalon
  • 4 Clinical Implications
  • References

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