Transcript Endoscopic Anatomy of the roof of the fourth

ENDOSCOPIC ANATOMY OF THE ROOF
OF THE FOURTH VENTRICLE:
QUALITATIVE AND QUANTITATIVE STUDY
Asem Salma, MD, Peter M. Sayers, BS, Nishanta B. Baidya, MD
Esmiralda Yeremeyeva, MD, Mario Ammirati, MD, MBA
Department of Neurological Surgery
The Ohio State University Medical Center, Columbus, Ohio
Disclosures
• Nothing to disclose
Background and Objective
• The anatomy of the roof of the IV ventricle has
received less attention compared to its floor, and
has rarely been thoroughly discussed in the
neurosurgical literature.
• As the use of the endoscope is becoming more
popular as an adjunct to microsurgical
techniques we conducted an anatomical
investigation of the endoscopic appearance of
the roof of the IV ventricle to demonstrate its
endoscopic features
Materials & Methods
• We explored the IV ventricle in 8 cadaveric heads by using 2.7
mm and 4 mm (0 degree and 30 degree angles) rigid
endoscopes. The endoscopic anatomical features of the IV
ventricle were extensively studied and documented using
imaging capture and recording.
• In addition we made 7 casts of the IV ventricle and measured
the caudal diameter of the aqueduct, the length of the
superior cerebellar peduncles and the distance between the
farthest separations of these two peduncles
Results
Qualitative Analysis
General overview
• The roof the IV ventricle can be looked at as an anatomical complex structure
with unique geometrical configuration. It consists of lateral portions which form
bilateral pillars for the midline portion (the medullary vela). The lateral portion is
formed by the cerebellar peduncles (superior, inferior and middle), and the midline
portion is formed by the superior and inferior medullary velum.
• The roof can be divided into three zones; the upper, middle and inferior, and
every zone corresponds to a specific lobe of the cerebellum.
• The upper zone is associated with the anterior lobe of the cerebellum. Here the roof is
formed by the superior cerebellar peduncles as the lateral component and an intervening
bridge (superior medullar velum) in between the two superior peduncles across the
midline. In the uppermost part the superior cerebellar peduncles converge toward the
midline.
Figure A, the upper zone. Endoscopic view of the roof of the IV
ventricle. Superior cerebellar peduncles (SP); superior medullary
velum (SMV); cerebral aqueduct (Aq).
• The middle zone is associated with the posterior cerebellar lobe. Here the roof is
represented by the inferior cerebellar peduncles as the lateral component and the
inferior medullary velum as the midline component which creates an intervening
bridge in between the two inferior peduncles.
Figure B, the middle zone. Endoscopic view of the roof of the IV ventricle. Superior
cerebellar peduncles (SP); superior medullary velum (SMV); inferior medullary
velum (IMV); inferior cerebellar peduncle (IP).
• The lower zone is associated with the flocculonodular lobe. Here the roof consists of the tela choroidea
and choroid plexus. In this region, the tela choroidea creates both the midline component and the lateral
components, as the arrangement of the cerebellar peduncles changes from their lateral orientation into
an anterolateral orientation. The tela choroidea extends from the inferior peduncle (anteromedial) and
the middle peduncle (anterolateral) posteriorly and downward to reach the taenia of the IV ventricle.
Figure C, the lower zone. Endoscopic view of the lower zone of the roof of the fourth ventricle.
Superior cerebellar peduncles (SP); inferior cerebellar peduncle (IP); lateral recess (LR). The right
view shows the lowermost part of this zone.
Quantitative Analysis
• We made 7 silicone casts of the IV ventricle and took the measurement as shown in Table 1. However
we were unable to get the casts of the lower portion of the roof because the casts that filled the crevices
of the tela choroidea and choroid plexus were very fragile and hence that would easily give away
whenever we would try recover the casts from inside the ventricle.
Anatomical Landmarks
Minimum
Mean ± SD
Maximum
Median
Diameter of the Aqueduct
2.78 ± 0.47
3.5
3.0
2.0
Superior Cerebellar Peduncle
25.92 ± 0.78
27.0
26.0
25.0
Distance between the farthest distal ends of
the superior cerebellar peduncles
(width of the fastigium)
17.78 ± 0.84
19.0
18.0
16.5
Table 1. The table shows the mean values ± standard deviation (SD) of different anatomical
landmarks of the seven IV ventricle silicone casts with the maximum, minimum and median values for
those landmarks. All measurements are in mm.
Conclusions
• Having a through knowledge of the endoscopic
anatomical characteristics of the roof of the fourth
ventricle may be helpful in purely endoscopic or
endoscopic assisted approaches to the IV ventricle.