•
•
Neuroradiology
The Great Horizontal Fissure of the Cerebellum: Angiographic Appearance 1 Joachim F. Seeger, M.D., John F. Hemmer, M.D., and Ronald G. Quisling, M.D. The anatomy and ang iographic appearance of the great hor izontal fissure is seen on most vertebral angiograms of excellent quality and is best shown on the lateral and AP (transfacial) projections . Identification of the fissure may provide an additional angiographic landmark for precise localization of peripherally situated masses, either within or adjacent to the cerebellum. INDEX TERMS:
Brain , anatomy. Cerebellum. Cerebral blood vessels, anatomy
Radiology 117:321-327, November 1975
•
• UADRANGULAR LOBUL E ( Anterior por t )
horizontal fissure (GHF) or horizontal sulcus of the cerebellum represents a landmark which divides the cerebellar hemispheres into superior and inferior portions. In our experience, the fissure can be visualized on most selective vertebral angiograms of excellent quality. Despite this fact, very little has appeared in the literature on the angiographic appearance of the GHF. Mani et al. (5) showed the fissure on an injection specimen of the superior cerebellar artery (SCA) and Huang and Wolf (3) demonstrated vessels within the fissure on an injection specimen of the posterior inferior cerebellar artery (PICA). Recently, Savoiardo and Passerini (7) described visualization of branches of the PICA within the GHF as an unusual angiographic finding . We feel that the angiographic appearance of the GHF may serve as an aid in the precise localization of a mass lesion within or adjacent to the peripheral or lateral aspect of the cerebellar hemisphere. The purpose of this paper is twofold : (a) to correlate the gross and angiographic anatomy of the GHF; and (b) to show the effect upon the fissure by adjacent mass lesions.
T
HE GREAT
PRIMARY FISSURE
QU QUADRANGULAR LOBUL E (Poster ior port )
POSTCLI VAL F ISSURE SU SUPERIOR SEISEMILUNAR LI LOBULE
UNNAMED FISSURE
AA
INF ERIOR SEMIL UNAR LOBUL E
GREAT HORIZONAL F ISSURE POSTCLIVAL F ISSU RE
QUADRANGULAR LOBULE
SUPER IOR SEM ILUNAR LOBULE
MATERIAL AND METHOD
FLOCCULUS
Frequency of visualization and angiographic anatomy of the GHF were assessed by reviewing 50 normal vertebral angiograms. All examinations were performed by selective vertebral artery catheterization from the femoral route. Lateral, half-axial (Towne), and straight anteroposterior (transtacial) projections were obtained in all cases. Subtraction was used in each case and magnification filming was employed in several examinations, usually in the lateral projection. Additional anatomic information was derived from gross dissection of 10 brains (20 cerebellar hemispheres). Particular attention was given to identification of major and minor contributors to the arterial network within the GHF.
8 QUADRANGULAR LOBUL E (Ante r ior part)
NODULUS PONT IS
QLQUADRANGUL AR LOBUL E ( Pcsteri or part) POSTCLI VAL F ISSURE
c
TONSIL BI VENTRAL ..LCLaUL E
Fig. 1. Semischematic drawings of the cerebellum, showing the great horizontal fissure (GHF) and its relationship to adjacent structures. A. Posterior view. B. Lateral view . C. Anterior view (brainstem removed) . 1, A and C depict the cerebellum as seen in the angiographic AP transtaclal projection.
ANATOMIC DESCRIPTION
The GHF originates posteriorly as a shallow midline
1 From the Department of Radiology, Neuroradiology Section, University of Michigan Medical Center, Ann Arbor, MI. Accepted for publication in June 1975 . Supported in part by a Special Fellowship in Neuroradiology (R. G. C.) F11NS57-73 from the National Institute of Neurological Diseases and Stroke. elk
321
322
JOACHIM F. SEEGER AND OTHERS
November 1975
~
.
A
L
B
c
L
Fig. 2. Vertebral angiogram In a 37-year-old woman with mild Chlari malformation. A. Lateral view demonstrates the characteristic appearance of the GHF of each hemisphere (A 'f'), in this case not completely superimposed. B. The occipital aspect of the GHF is seen in the Towne projection, def ined by points of abrupt angulation of penetrating hem ispher ic branches of the PICAs ('f'). C. The transfacial view opt imally demonstrates the occipital aspects of the GHF ('f'). On the right, the lateral AICA branch of an AICAPICA trunk passes from the petrosal to the occipital aspect of the fissure (C:).
groove between the folium and tuber vermis (Fig. 1, A). It passes along the occipital surface of each cerebellar hemisphere just below the posterolateral margin of the cerebellum as a deep sulcus, bordered by the superior and inferior semilunar lobules (Fig. 1, B). Upon reaching the anterior or petrosal surface of the cerebellum, the GHF is bordered by the posterior quadrangular lobule above and the inferior semilunar lobule (gracile) below (Fig . 1, C). The fissure widens as it approaches its termination along the outer surface of the brachium pontis, the anterior quadrangular lobule forming its upper margin and the flocculus its lower border (2, 4).
Anatomic dissections revealed a network of small arteries and arterioles within the GHF. This is also shown in Bassett's atlas (1). The posterior inferior cerebellar artery (PICA) usually was the major contributor to this vascular plexus. Cortical branches ascending over the surface of the biventer and inferior semilunar lobule either passed into the fissure directly or initially paralleled the fissure for variable distances. A prominent tributary of the inferior vermian branch of the PICA occasionally penetrated the posteromedial aspect of the GHF. More laterally, the marginal branch of the superior cerebellar artery (SCA) sent a major branch into the fissure in one
Vol. 117
GREA T HORIZONTAL FISSURE OF
fourth of the specimens and a minor branch in approximately a third. Occasionally one or more cortical (hemispheric) branches of the SCA, after randomly crossing the superior surface of the hemisphere, extended onto the upper portion of the occipital surface and terminated in the GHF. In one fourth of the specimens, the anterior or petrosal aspect of the fissure received a major tributary from the lateral branch of the anterior inferior cerebellar artery (AICA). Smaller branches of the AICA passing into the fissure were seen in half of the specimens. Although interfoliar rami of the SCA and also of the PICA were seen in fissures other than the GHF, they were never as prominent as those within the GHF in any of our specimens.
THE
CEREBELLUM
323
NeuroradioJogy
;:
"
ANGIOGRAPHIC ANATOMY
Of the three projections usually employed for vertebral angiography in our institution, the lateral and AP .(transfacial) views are by far the most useful for evaluation of the GHF. since the central beam is nearly parallel to the arterial plexus within the fissure in both projections (Fig. 2). The GHF is most readily identified on the lateral view during the mid-to-late arterial phase, when contrastfilled small arteries and arterioles within the fissure meld into a discrete linear "stain" (Fig. 3), which often can be identified easily, even without subtraction. In the earlier arterial phase, the GHF is usually outlined by multiple points of abrupt alteration in the course of cerebellar hemispheric arteries, reflecting entry of these vessels into the fissure (Fig . 4). Extrapolated to skull landmarks, the normal GHF typically falls on a line connecting the
L Fig. 3. Lateral view during the capillary phase demonstrates the GHF (il and its relationship to the superior vermis and inferior hemisphere (i >. and to the posterior angle of the cerebellum (0).
internal occipital protuberance and the external audltory meatus, usually with a mild posteroinferior convexity. The most posterior aspect of the fissure always projects just below the junction of the tentorial and occipital surfaces of the cerebellar hemisphere on lateral projection (Fig. 3). The GHF was identified on lateral projection in 84 % of our 50 normal vertebral angiograms (TABLE I).
Fig. 4. Normal vertebral ang iogram in a 6-year-old boy . A. Lateral view. B. Towne projection. In this case the superior cerebellar arteries are the domlna.nt contributors to the GHF ( .. ) via right and left (0) marginal branches and right (i> and left hemispheric branches. Left PICA branches f6f) also pass into the fissure .
C+>
324
JOACHIM
F.
SEEGER AND OTHERS
November 1975
Table I: Frequency of V isualization of GHF i n 50 Normal Selective Vertebral Ang iograms Lateral Project ion AP Projection, with reflu x (37 cases) Bilateral visualization Un ilateral visualization Nonvisualization AP Projection, w ithout reflu x (13 cases) Bilateral visual ization Un ilateral v isualization Nonvisualization
.-
42/50
(84%)
34 0 3
(92%) (8%)
0 13
(100%)
0
Table II : Angiographic Identification of Source of Vascular Network Within GHF in 50 Normal Selective Vertebral Angiograms* Major source" Minor source" PICA t AICA AICA-PICA Trunk SCA
L Fig. 5. Normal vertebral angiogram in a 12-yea r-old girl. The transfacial view shows striking symmetry of the vascularity of the cerebellar hemispheres. Close scrutiny allows identification of the entire GHF on each side by following the lateral AICA branches (
•
Neuroradiology
The Great Horizontal Fissure of the Cerebellum: Angiographic Appearance 1 Joachim F. Seeger, M.D., John F. Hemmer, M.D., and Ronald G. Quisling, M.D. The anatomy and ang iographic appearance of the great hor izontal fissure is seen on most vertebral angiograms of excellent quality and is best shown on the lateral and AP (transfacial) projections . Identification of the fissure may provide an additional angiographic landmark for precise localization of peripherally situated masses, either within or adjacent to the cerebellum. INDEX TERMS:
Brain , anatomy. Cerebellum. Cerebral blood vessels, anatomy
Radiology 117:321-327, November 1975
•
• UADRANGULAR LOBUL E ( Anterior por t )
horizontal fissure (GHF) or horizontal sulcus of the cerebellum represents a landmark which divides the cerebellar hemispheres into superior and inferior portions. In our experience, the fissure can be visualized on most selective vertebral angiograms of excellent quality. Despite this fact, very little has appeared in the literature on the angiographic appearance of the GHF. Mani et al. (5) showed the fissure on an injection specimen of the superior cerebellar artery (SCA) and Huang and Wolf (3) demonstrated vessels within the fissure on an injection specimen of the posterior inferior cerebellar artery (PICA). Recently, Savoiardo and Passerini (7) described visualization of branches of the PICA within the GHF as an unusual angiographic finding . We feel that the angiographic appearance of the GHF may serve as an aid in the precise localization of a mass lesion within or adjacent to the peripheral or lateral aspect of the cerebellar hemisphere. The purpose of this paper is twofold : (a) to correlate the gross and angiographic anatomy of the GHF; and (b) to show the effect upon the fissure by adjacent mass lesions.
T
HE GREAT
PRIMARY FISSURE
QU QUADRANGULAR LOBUL E (Poster ior port )
POSTCLI VAL F ISSURE SU SUPERIOR SEISEMILUNAR LI LOBULE
UNNAMED FISSURE
AA
INF ERIOR SEMIL UNAR LOBUL E
GREAT HORIZONAL F ISSURE POSTCLIVAL F ISSU RE
QUADRANGULAR LOBULE
SUPER IOR SEM ILUNAR LOBULE
MATERIAL AND METHOD
FLOCCULUS
Frequency of visualization and angiographic anatomy of the GHF were assessed by reviewing 50 normal vertebral angiograms. All examinations were performed by selective vertebral artery catheterization from the femoral route. Lateral, half-axial (Towne), and straight anteroposterior (transtacial) projections were obtained in all cases. Subtraction was used in each case and magnification filming was employed in several examinations, usually in the lateral projection. Additional anatomic information was derived from gross dissection of 10 brains (20 cerebellar hemispheres). Particular attention was given to identification of major and minor contributors to the arterial network within the GHF.
8 QUADRANGULAR LOBUL E (Ante r ior part)
NODULUS PONT IS
QLQUADRANGUL AR LOBUL E ( Pcsteri or part) POSTCLI VAL F ISSURE
c
TONSIL BI VENTRAL ..LCLaUL E
Fig. 1. Semischematic drawings of the cerebellum, showing the great horizontal fissure (GHF) and its relationship to adjacent structures. A. Posterior view. B. Lateral view . C. Anterior view (brainstem removed) . 1, A and C depict the cerebellum as seen in the angiographic AP transtaclal projection.
ANATOMIC DESCRIPTION
The GHF originates posteriorly as a shallow midline
1 From the Department of Radiology, Neuroradiology Section, University of Michigan Medical Center, Ann Arbor, MI. Accepted for publication in June 1975 . Supported in part by a Special Fellowship in Neuroradiology (R. G. C.) F11NS57-73 from the National Institute of Neurological Diseases and Stroke. elk
321
322
JOACHIM F. SEEGER AND OTHERS
November 1975
~
.
A
L
B
c
L
Fig. 2. Vertebral angiogram In a 37-year-old woman with mild Chlari malformation. A. Lateral view demonstrates the characteristic appearance of the GHF of each hemisphere (A 'f'), in this case not completely superimposed. B. The occipital aspect of the GHF is seen in the Towne projection, def ined by points of abrupt angulation of penetrating hem ispher ic branches of the PICAs ('f'). C. The transfacial view opt imally demonstrates the occipital aspects of the GHF ('f'). On the right, the lateral AICA branch of an AICAPICA trunk passes from the petrosal to the occipital aspect of the fissure (C:).
groove between the folium and tuber vermis (Fig. 1, A). It passes along the occipital surface of each cerebellar hemisphere just below the posterolateral margin of the cerebellum as a deep sulcus, bordered by the superior and inferior semilunar lobules (Fig. 1, B). Upon reaching the anterior or petrosal surface of the cerebellum, the GHF is bordered by the posterior quadrangular lobule above and the inferior semilunar lobule (gracile) below (Fig . 1, C). The fissure widens as it approaches its termination along the outer surface of the brachium pontis, the anterior quadrangular lobule forming its upper margin and the flocculus its lower border (2, 4).
Anatomic dissections revealed a network of small arteries and arterioles within the GHF. This is also shown in Bassett's atlas (1). The posterior inferior cerebellar artery (PICA) usually was the major contributor to this vascular plexus. Cortical branches ascending over the surface of the biventer and inferior semilunar lobule either passed into the fissure directly or initially paralleled the fissure for variable distances. A prominent tributary of the inferior vermian branch of the PICA occasionally penetrated the posteromedial aspect of the GHF. More laterally, the marginal branch of the superior cerebellar artery (SCA) sent a major branch into the fissure in one
Vol. 117
GREA T HORIZONTAL FISSURE OF
fourth of the specimens and a minor branch in approximately a third. Occasionally one or more cortical (hemispheric) branches of the SCA, after randomly crossing the superior surface of the hemisphere, extended onto the upper portion of the occipital surface and terminated in the GHF. In one fourth of the specimens, the anterior or petrosal aspect of the fissure received a major tributary from the lateral branch of the anterior inferior cerebellar artery (AICA). Smaller branches of the AICA passing into the fissure were seen in half of the specimens. Although interfoliar rami of the SCA and also of the PICA were seen in fissures other than the GHF, they were never as prominent as those within the GHF in any of our specimens.
THE
CEREBELLUM
323
NeuroradioJogy
;:
"
ANGIOGRAPHIC ANATOMY
Of the three projections usually employed for vertebral angiography in our institution, the lateral and AP .(transfacial) views are by far the most useful for evaluation of the GHF. since the central beam is nearly parallel to the arterial plexus within the fissure in both projections (Fig. 2). The GHF is most readily identified on the lateral view during the mid-to-late arterial phase, when contrastfilled small arteries and arterioles within the fissure meld into a discrete linear "stain" (Fig. 3), which often can be identified easily, even without subtraction. In the earlier arterial phase, the GHF is usually outlined by multiple points of abrupt alteration in the course of cerebellar hemispheric arteries, reflecting entry of these vessels into the fissure (Fig . 4). Extrapolated to skull landmarks, the normal GHF typically falls on a line connecting the
L Fig. 3. Lateral view during the capillary phase demonstrates the GHF (il and its relationship to the superior vermis and inferior hemisphere (i >. and to the posterior angle of the cerebellum (0).
internal occipital protuberance and the external audltory meatus, usually with a mild posteroinferior convexity. The most posterior aspect of the fissure always projects just below the junction of the tentorial and occipital surfaces of the cerebellar hemisphere on lateral projection (Fig. 3). The GHF was identified on lateral projection in 84 % of our 50 normal vertebral angiograms (TABLE I).
Fig. 4. Normal vertebral ang iogram in a 6-year-old boy . A. Lateral view. B. Towne projection. In this case the superior cerebellar arteries are the domlna.nt contributors to the GHF ( .. ) via right and left (0) marginal branches and right (i> and left hemispheric branches. Left PICA branches f6f) also pass into the fissure .
C+>
324
JOACHIM
F.
SEEGER AND OTHERS
November 1975
Table I: Frequency of V isualization of GHF i n 50 Normal Selective Vertebral Ang iograms Lateral Project ion AP Projection, with reflu x (37 cases) Bilateral visualization Un ilateral visualization Nonvisualization AP Projection, w ithout reflu x (13 cases) Bilateral visual ization Un ilateral v isualization Nonvisualization
.-
42/50
(84%)
34 0 3
(92%) (8%)
0 13
(100%)
0
Table II : Angiographic Identification of Source of Vascular Network Within GHF in 50 Normal Selective Vertebral Angiograms* Major source" Minor source" PICA t AICA AICA-PICA Trunk SCA
L Fig. 5. Normal vertebral angiogram in a 12-yea r-old girl. The transfacial view shows striking symmetry of the vascularity of the cerebellar hemispheres. Close scrutiny allows identification of the entire GHF on each side by following the lateral AICA branches (
