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original papers
Adv Clin Exp Med 2011, 20, 3, 351–361
ISSN 1230-025X
© Copyright by Wroclaw Medical University
Barbara Hendrich1, Krzysztof Zimmer2, Maciej Guziński1, Marek J. Sąsiadek1
Application of 64-Detector Computed Tomography
Myelography in the Diagnostics of the Spinal Canal
Zastosowanie 64-rzędowej mielografii tomografii komputerowej
w diagnostyce kanału kręgowego
Department of General and Interventional Radiology and Neuroradiology, Chair of Radiology, Wroclaw
Medical University, Poland
2
Department of Traumatic and Hand Surgery, Wroclaw Medical University, Poland
1
Abstract
Background. The most important imaging modality of the spine and spinal canal is magnetic resonance (MRI). In
a relatively large group of patients with contraindications to MR, the alternative method is computed tomography
myelography (myelo-CT). The development of multi-detector spiral CT, especially 64-detector scanners, could
potentially increase the diagnostic possibilities of myelo-CT.
Objectives. Evaluation of usefulness of 64-detector myelo-CT in diagnostics of the spinal canal.
Material and Methods. Myelo-CT studies were performed with a 64-detector CT scanner in 31 patients (29 males,
2 females, age 17–71, mean age 31.9). The patients were referred with diagnoses of brachial plexus injury (27 cases),
spinal canal stenosis (2 cases), suspected communication with fluid space in sacral region (1 case), and suspected
intraspinal lesions after vertebral stabilization (1 case). A contrast medium (300 mg iodine/ml) was injected into the
dural sac via sucoccipital (14 patients) or lumbar (17 patients) puncture. After that, a spiral acquisition (slice thickness 0.625 mm, pitch 0.9) was performed with a 64-detector CT scanner, followed by multiplanar MIP (Maximum
Intensity Projection) reconstruction. In 26 patients, a comparison with operative results was performed.
Results. Among the 27 patients with traumatic injury of the brachial plexus, nerve root lesions were revealed
(preganglionic brachial plexus injury) in 14 patients, and in 13 cases myelo-CT was normal (postganglionic injury).
In the 4 patients referred with diagnoses other than brachial plexus injury, myelo-CT contributed to therapeutic
decisions, e.g. of reoperation in the patient with intraspinal haematoma, diagnosed on the basis of the myelo-CT
scan. In the 14 patients with the features of preganglionic brachial plexus injury in myelo-CT, we analyzed C5-T1
nerve roots in detail on the side of the injury (overall 140 roots). We found a lack of the outlines or continuity of
57 roots in 13 patients. Intraoperatively, 53 roots were verified, confirming their injury in 49 cases (92.5%).
Conclusions. 64-detector CT myelography enables an efficient assessment of the spinal canal space in patients with
contraindications to MR, especially visualization of nerve root injury (Adv Clin Exp Med 2011, 20, 3, 351–361).
Key words: myelography, spiral computed tomography, brachial plexus, spinal injuries.
Streszczenie
Wprowadzenie. Najważniejszą metodą obrazową kręgosłupa i kanału kręgowego jest rezonans magnetyczny (MR).
U dość licznej grupy pacjentów z przeciwwskazaniami do MR alternatywnym badaniem jest mielografia tomografii
komputerowej (mielo-TK). Rozwój spiralnej tomografii komputerowej wielorzędowej, w szczególności 64-rzędowej, budzi nadzieje na zwiększenie możliwości diagnostycznych mielo-TK.
Cel pracy. Ocena przydatności 64-rzędowej mielo-TK w diagnostyce kanału kręgowego.
Materiał i metody. Badania mielo-TK wykonano za pomocą aparatu 64-rzędowego, u 31 pacjentów (29 mężczyzn,
2 kobiety, wiek 17–71, średnio 31,9 roku). Pacjenci byli kierowani z rozpoznaniem uszkodzenia splotu ramiennego
(27 chorych), stenozy kanału kręgowego (2 pacjentów), podejrzenia komunikacji z przestrzenią płynową w okolicy
krzyżowej (1 pacjent), podejrzenia zmian wewnątrzkanałowych po stabilizacji kręgosłupa (1 pacjent). Środek kontrastowy (300 mg jodu/ml) podawano do przestrzeni podpajęczynówkowej drogą nakłucia podpotylicznego (14 pacjentów)
lub lędźwiowego (17 pacjentów). Za pomocą 64-rzędowego skanera wykonywano akwizycję spiralną (grubość warstwy
0,625 mm, skok spirali 0,9). Podczas postprocessingu uzyskiwano rekonstrukcje wielopłaszczyznowe MIP (Maximum
Intensity Projection). Przeprowadzono analizę porównawczą z wynikami śródoperacyjnymi u 26 pacjentów.
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B. Hendrich et al.
Wyniki. Wśród 27 pacjentów z urazowym uszkodzeniem splotu ramiennego u 14 stwierdzono cechy uszkodzenia korzeni nerwowych (uszkodzenie przedzwojowe splotu), w 13 przypadkach z tej grupy obraz mielo-TK był
prawidłowy (uszkodzenie pozazwojowe). U 4 chorych, u których mielo-TK została wykonana ze wskazań innych
niż uszkodzenie splotu ramiennego, badanie to pomogło podjąć decyzje terapeutyczne, np. o reoperacji u pacjenta z rozpoznanym na podstawie mielo-TK krwiakiem w kanale kręgowym. U 14 chorych z cechami uszkodzenia przedzwojowego splotu ramiennego w mielo-TK szczegółowej ocenie poddano korzenie nerwowe C5-Th1
po stronie uszkodzonej (łącznie 140 korzeni). Wykazano brak zarysu lub ciągłości 57 korzeni u 13 pacjentów.
Śródoperacynie zweryfikowano 53 korzenie, potwierdzając ich uszkodzenie w 49 przypadkach (92,5%).
Wnioski. 64-rzędowa mielografia TK pozwala na skuteczną ocenę przestrzeni wewnątrzkanałowej u pacjentów
z przeciwwskazaniami do MR, a zwłaszcza uwidocznienie uszkodzenia korzeni nerwowych (Adv Clin Exp Med
2011, 20, 3, 351–361).
Słowa kluczowe: mielografia, spiralna tomografia komputerowa, splot ramienny, uszkodzenie kręgosłupa.
The most important role in diagnostic imaging
of the spine and spinal canal is currently played by
magnetic resonance (MRI) [1–5]. This technique
allows for comprehensive assessment of the spinal
canal, vertebrae, intervertebral discs, fluid spaces
within the canal and perivertebral structures. However, there is still quite a large number of patients
in whom magnetic resonance cannot be applied
due to contraindications related to ferromagnetic
implants and stabilizers, pacemakers etc.
With this group of patients other techniques
may be applied, especially computed tomography
and, in the case of assessment of fluid spaces of
the spine, CT myelography [6]. With the development of multi-detector spiral computed tomography and especially the introduction of 16-, or even
64-detector devices, which provide imaging with
submillimeter resolution in all planes, the quality
of CT scans of different regions of the body has
improved significantly [7–12]. This raises hopes
for the increased diagnostic potential of CT myelography studies as well.
In the Department of General and Interventional Radiology and Neuroradiology, School of Radiology, Wroclaw Medical University, myelographic
studies (MR myelography and CT myelography)
are performed routinely on patients who require
assessment of posttraumatic injury of the brachial
plexus. The modality of choice is MR myelography,
an entirely non-invasive technique based on strong
T2-weighing which provides so-called MR hydrography, similar as in the case of magnetic resonance
cholangiopancreatography (MRCP) or MR urography [13, 14]. In patients with contraindications
to MR, CT myelography is performed. Despite the
development of digital radiography, the previously
applied conventional X-ray myelography has been
almost entirely abandoned [6, 15].
The aim of the paper is to assess the usefulness of 64-detector CT myelography in diagnostics
of the spinal canal and especially the verification
of indications to high resolution CT myelography
and the definition of new standards of performance
and assessment of scans by a 64-detector device.
Material and Methods
Between December 2007 and January 2010,
CT myelography was performed with a 64-detector scanner in 31 patients (29 men and 2 women),
aged from 17 to 71 (mean age: 31.9). All the patients
had contraindications to magnetic resonance – in
most cases ferromagnetic components of fractured
bone unions.
Injury to the brachial plexus with suspected
tearing of nerve roots from the spinal cord was by
far the most frequent indication to CT myelography (27 out of 31 patients). In two patients the
aim of the examination was to assess the degree of
spinal stenosis and dural sac compression before
an operation. In another patient the examination
was performed to assess possible communication
between a pathological fluid space in the sacral region and the dural sac. In one case the examination assessed changes in the spinal canal early after
surgical stabilization of the spine.
Patients were administered 10–15 ml of a contrast medium of 300 mg of iodine/ml by suboccipital (in 14 cases) or lumbar (in 17 patients) injection.
The puncture site was selected by a neuroradiologist after assessment of anatomical conditions. The
puncture was done with a 19G puncture needle
guided by radiography in the Intervention Radiology Section and then the patient was taken to the
CT Section. The patients with a lumbar puncture
were laid on one side with hips elevated for a couple of minutes (a wedge-shaped hip support was
used). Patients who received contrast medium via
suboccipital puncture were put on the computed
tomography table immediately. For scanning, they
lay supine, arms along the trunk. A pilot scan of the
section of the spine with the suspected lesion was
performed to define the area of interest. In the case
of assessment of subarachnoid space in patients
with a suspected tear of nerve roots from the spinal cord, the area of interest included the area between mid C2 vertebra to intervertebral space T2/
T3. In the remaining cases the scope of scanning
depended on the clinical problem. Then, a 64-de-
Application of 64-Detector CT Myelography
tector scanner was applied to perform spiral acquisition (slice thickness 0.625 mm, pitch 0.9, lamp
rotation 0.5 s average). Each time, an automated
selection of lamp current was applied (intensity
modulation). Radiation doses depended mainly on
the scope of the examination, ranging from 700 to
1500 DLP (Dose Length Product) (1000 DLP average). Post-processing included multi-plane MIP
reconstructions (Maximum Intensity Projection).
The images were assessed in soft-tissue and bone
windows.
After the examination, the patients were taken
to a clinical ward in supine position. In the case
of patients after a lumber puncture, typical indications after a lumbar puncture were applied. Patients after a suboccipital puncture were advised
to remain in a half-sitting position for 6 hours. In
one patient, a weak post-puncture syndrome was
observed and was treated in a routine way (supine
position and fluid therapy for 24 hours). In the remaining cases no side effects were noted.
The results were assessed at AW4.4 working
stations. MIP reconstructions of transverse scans
were analyzed in at least two windows: the soft
tissue window and close to the bone window. In
our opinion this is the best way to visualize nerve
roots against the contrasting cerebrospinal fluid.
Coronal, sagittal and oblique MIP reconstructions
were used for the best comparison of the healthy
side and the affected one. Levels on which nerve
root injuries were revealed were analyzed in detail
in transverse sections. Roots that are comprised in
the brachial plexus were assessed, i.e ventral and
dorsal C5, C6, C7, C8 and T1 roots on the affected
side, dividing the brachial plexus into the upper
part (C5 and C6 roots), medial part (C7 root) and
lower part (C8 and T1 roots).
Normal appearance was defined as an intact
outline of roots, a symmetric course of roots as
compared to the contralateral plexus, symmetric
contours of the dural sac and medial location of
the spinal cord within the dural sac.
If lesions were detected in the CT myelography, the direct features of the injury were assessed,
including a lack of outline or continuity of the
root and displacement of the cord within the dural sac toward the affected side due to the drawing
force affecting the upper limb (avulsion injury)
(Fig. 1 a, b). The image of nerve roots on the affected side was assessed by comparison to nerve roots
on the same level on the uninvolved side (Fig. 2 a,
b). The assessment concerned the presence of outlines of both dorsal and ventral roots. If an outline
of none of the two roots was found on a given level,
the result was classified as a tear of 2 roots.
The assessment also concerned the location of
pseudocysts in relation to the dural sac, interverte-
353
a
b
Fig. 1. Patient with symptoms of injury of the left
brachial plexus. CT myelography (a – coronal plane,
b – transverse plane) shows no outline of C7 and C8
roots on the left and a small pseudocyst on the C6/C7
level (a), while on the opposite side all roots are visible.
Spinal cord is displaced to the left and slightly posteriorly (b)
Ryc. 1. Pacjent z objawami uszkodzenia lewego splotu
ramiennego. W mielo-TK (a – płaszczyzna czołowa,
b – płaszczyzna poprzeczna) stwierdza się brak zarysu
korzeni C7 i C8 po stronie lewej oraz niewielką torbiel
rzekomą na wysokości C6/C7 (a). Rdzeń kręgowy jest
przemieszczony w lewo i nieco ku tyłowi (b)
354
B. Hendrich et al.
a
a
b
Fig. 2. CT myelography, coronal plane: a – lack of outline of C6, C7, C8 and T1 nerve roots on the left, small
pseudocyst of the T1 root. Transverse scan: b – lack
of root contours on the left, dural sac compressed by
a pseudocyst
Ryc. 2. Mielo-TK w płaszczyźnie czołowej (a): brak
zarysu korzeni nerwowych C6, C7, C8, Th1 po stronie
lewej, mała torbiel rzekoma korzenia Th1. Obraz
w płaszczyźnie poprzecznej (b): brak rysunku korzeni
po stronie lewej, torbiel rzekoma uciska worek oponowy
b
Fig. 3. CT myelography (two different patients):
a – two large pseudocysts on the C6/C7 and C7/T1
levels in the spinal canal and intervertebral foramina,
b – irregular contours of the dural sac on the left
Ryc. 3. Mielo-TK (dwóch różnych pacjentów): a – dwie
duże torbiele rzekome na poziomach C6/C7 i C7/Th1
w kanale kręgowym i otworach międzykręgowych,
b – nierówne obrysy worka oponowego po stronie
lewej
Initials
(Inicjały)
ŁP
ŁJ
JA
CS
OP
PK
KD
CM
DD
GłM
GraM
WR
JR
RP
SK
TM
PZ
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
37
47
22
19
36
17
22
60
26
29
27
24
25
29
25
71
20
Age
(Wiek)
0
2
0
0
0
0
0
2
1
0
0
2
2
2
2
0
2
1
2
0
0
2
2
0
cyst in l-s section
no tear
2
0
no tear
0
no tear
2
0
2
assessment of the spinal canal
spinal stabilisation
0
2
0
0
0
0
cervical stenosis
no tear
C8
2
0
2
0
2
2
0
0
0
Th1
4
0
0
0
4
0
0
0
0
2
2
0
0
2
1
0
0
2
middle
part
(część
środkowa)
upper
part
(część
górna)
C7
C5
C6
Plexus injury
(Uszkodzenie splotu)
Lack of root outline
(Brak zarysów korzeni)
Tabela 1. Wyniki badania mielo-TK i zgodność z oceną śródoperacyjną
Table 1. Results of CT myelography and correlation with intraoperative findings
4
0
4
2
4
4
0
2
1
lower
part
(część
dolna)
5
1
1
3
5
3
5
1
2
number of
pseudocysts
(liczba pseudotorbieli)
Other disorder
(Inna patologia)
yes
yes
stenosis
(stenoza)
yes
yes
yes
spondylosis
(spondylioza)
yes
yes
yes
yes
yes
traction and
spinal cord displacement
(trakcja i przemieszczenie
rdzenia)
conformity
conformity
conformity
conformity
conformity
partial conformity
conformity
no surgery
conformity
conformity
conformity
partial conformity
conformity
no surgery
partial conformity
no data
Conformity
Conformity with
intraprocedural assessment
(Zgodność z oceną
śródoperacyjną)
Application of 64-Detector CT Myelography
355
J-ZA
TD
LK
SS
KJ
FM
MR
GruM
BT
ŻA
FS
WR
PJ
19
20
21
22
23
24
25
26
27
28
29
30
31
TOTAL
Initials
(Inicjały)
No.
54
50
20
22
26
19
32
45
37
59
23
28
19
Age
(Wiek)
no tear
no tear
0
no tear
no tear
2
no tear
no tear
0
no tear
0
no tear
no tear
C5
0
2
0
0
C6
0
2
2
2
C7
Lack of root outline
(Brak zarysów korzeni)
0
0
0
0
C8
2
0
0
0
Th1
13
0
4
0
0
upper
part
(część
górna)
17
0
2
2
2
middle
part
(część
środkowa)
Plexus injury
(Uszkodzenie splotu)
Tabela 1. Wyniki badania mielo-TK i zgodność z oceną śródoperacyjną (cd.)
Table 1. Results of CT myelography and correlation with intraoperative findings (cd.)
27
2
0
0
0
lower
part
(część
dolna)
34
1
1
1
1
number of
pseudocysts
(liczba pseudotorbieli)
Other disorder
(Inna patologia)
3
yes
stenosis
(stenoza)
6
yes
yes
yes
spondylosis
(spondylioza)
7
yes
yes
traction and
spinal cord displacement
(trakcja i przemieszczenie
rdzenia)
conformity
conformity
no verification of
the level of lesions
conformity
conformity
conformity
conformity
conformity
partial conformity
conformity
partial conformity
no surgery
conformity
Conformity with
intraprocedural assessment
(Zgodność z oceną
śródoperacyjną)
356
B. Hendrich et al.
357
Application of 64-Detector CT Myelography
bral foramina, spinal canal and spinal cord as well as
irregular contours of the dural sac (Fig. 3 a, b, c). Indirect evidence of a tear of nerve roots from the spinal cord were considered, too, e.g. presence of pseudocysts and irregular contour of the cord [3, 4].
Other lesions within the cervical spine were
assessed too, e.g. fractures, degenerative lesions,
spinal canal stenosis and congenital disorders.
Out of the 31 patients, 26 were operated on
and in these cases the results were compared to
intraoperative data.
Results
The CT myelography results for 31 patients
and intraoperative verification for 26 of them are
presented in Table 1.
Among the 27 patients referred to CT myelography because of unilateral injury to the brachial plexus, evidence of damage to nerve roots
was found (preganglionic damage to the brachial
plexus) in 14. In the remaining 13 cases CT myelography was normal; in these cases, considering clinical findings, the damage was assessed as
postganglionic (peripheral). Twenty five patients
with traumatic injury of the brachial plexus were
operated on in the Department of Traumatic and
Hand Surgery, Wroclaw Medical University. The
operations confirmed entirely the preganglionic or
peripheral damage in 19 cases. In 5 patients, partial correlation was revealed, i.e. tear of nerve roots
was confirmed but the number of affected roots
found during the surgery was different than diagnosed by CT myelography (more in 4 patients and
less in 1 patient). In 1 patient (FS) the tear of T1
roots diagnosed by CT myelography (Fig. 4) was
not verified during the operation because there
was no surgical revision of the T1/T2 intervertebral foramen due to difficult access.
Complete conformation of lesions revealed
during the surgery and diagnosed by CT myelography was found in 2 patients operated on for
other reasons: the surgeries confirmed respectively
compression of the dural sac by a hematoma after stabilization and the presence of a cyst in the
sacro-lumbar spine.
Fourteen patients with symptoms of an injury
to the brachial plexus and lesions visible in CT
myelography underwent detailed evaluation of the
image of dorsal and ventral nerve roots of the section from the C4/C5 to the T1/T2 intervertebral
foramen on the affected side (140 roots overall).
Lack of the outline of nerve roots against the contrast medium and lack of continuity or deformation were found in 57 roots (13 in the upper plexus,
17 in the medium plexus and 27 in the lower plex-
a
b
Fig. 4. CT myelography, oblique (a) and transverse
(b) planes, shows a pseudocyst at the T1/T2 level on
the left, above, traction of the spinal cord toward the
intervertebral foramen is visible
Ryc. 4. W badaniu mielo-TK w płaszczyźnie skośnej
(a) i poprzecznej (b) na poziomie Th1/Th2 po stronie
lewej jest widoczna torbiel rzekoma, powyżej stwierdza
się przeciągnięcie rdzenia kręgowego w stronę otworu
międzykręgowego
us). In 3 patients (PK, JA and SD) tear of a single
(dorsal) root was diagnosed with ventral roots intact.
The data regarding intraoperative appearance
was obtained for 53 roots. Injury to 49 roots was
found during the surgeries (92.5%).
Thirty four pseudocysts were revealed with
the most frequent location within the spinal canal,
followed by intervertebral foramina (Figs 4–6).
358
B. Hendrich et al.
a
Fig. 6. CT myelography (coronal plane) shows pseudocysts located inside the spinal canal on C7/T1 and
T1/T2 levels and a very small pseudocyst on the C6/C7
level; at the latter level the outline of the root is visible
Ryc. 6. W badaniu mielo-TK (płaszczyzna czołowa)
są widoczne torbiele rzekome położone wewnątrzkanałowo na poziomach C7/Th1 i Th1/Th2 oraz bardzo
drobna torbiel rzekoma na poziomie C6/C7; na tym
ostatnim poziomie jest widoczny zarys korzenia
b
Fig. 5. CT myelography, sagittal (a) and transverse
(b) planes, inside the spinal canal, on the left, multiple
pseudocysts are visible with tortuous outlines of nerve
roots
Ryc. 5. Mielo-TK w płaszczyźnie strzałkowej (a)
i poprzecznej (b), wewnątrzkanałowo po stronie lewej
są widoczne liczne torbiele rzekome z kręto przebiegającymi zarysami korzeni nerwowych
Only one pseudocyst involved perivertebral soft
tissues. Usually the presence of a cyst was related
to lack of the outline of nerve roots in the spinal
canal (Fig. 7). In one patient (JA), continuity of the
nerve roots was visualized in the lumen of a pseudocyst (Fig. 8), but during the operation the roots
were found to be torn. In the case of patient OP,
although there was no direct evidence of a tear of
nerve roots from the spinal canal, multiple pseudocysts containing roots were found within the
canal.
In 3 cases, further evidence of root injury was
visible without their tear, i.e. asymmetrical course
of roots within the dural sac as compared to the
unaffected side (in two cases the diagnosis was
confirmed during the surgery, in one case there
was no intraoperative verification).
CT myelography also allowed for the diagnosis of other lesions in the cervical spine. Evidence
of a degenerative process in the cervical spine and
compression of the dural sac by spinal structures
were found in 6 patients (Fig. 9), spinal canal stenosis in 3 patients, Schmorl’s nodes in 2 patients,
vacuum signs in the intervertebral discs of 2 patients and vertebral fusion (Klippel-Feil syndrome)
in one patient. Furthermore, 3 patients were diagnosed with other posttraumatic injuries than root
tear: fractures of ribs, spinous processes, clavicle
and C6 vertebral body.
In patient DD, after spine stabilization surgery
due to a fracture, CT myelography enabled the
discovery of a hematoma that was compressing
Application of 64-Detector CT Myelography
359
Fig. 7. CT myelography (transverse plane) – a pseudocyst visible in the intervertebral foramen on the right,
no outline of roots ipsilaterally
a
Ryc. 7. Mielo-TK (płaszczyzna poprzeczna) – torbiel rzekoma jest widoczna w otworze międzykręgowym po stronie prawej, brak zarysu korzeni nerwowych po tej stronie
Fig. 8. CT myelography (coronal plane) shows a nerve
root in the lumen of an inferior pseudocyst. The root
is angulated in the distal section, during the surgery,
a root tear was revealed
Ryc. 8. Badanie mielo-TK w płaszczyźnie czołowej wykazuje w świetle niżej leżącej torbieli rzekomej obecność
korzenia nerwowego zagiętego kątowo w dystalnym
odcinku, śródoperacyjnie wykazano przerwanie korzenia
Fig. 9. CT myelography, sagittal (a) and transverse (b)
planes, severe cervical spondylosis, there is compression of the dural sac by osteophytes and intervertebral
discs, with narrowed lumen of the spinal canal, there
is gas in C4/C5 and C5/C6 intervertebral discs as evidence of degeneration of the discs
Ryc. 9. Mielo-TK w płaszczyźnie strzałkowej (a)
i poprzecznej (b), zaawansowana spondyloza szyjna, widoczny ucisk na worek oponowy wywierany
przez osteofity i krążki międzykręgowe oraz zwężenie
światła kanału kręgowego, gaz w krążkach międzykręgowych C4/C5, C5/C6 – wyraz zwyrodnienia tych
krążków
b
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B. Hendrich et al.
the dural sac: this was the basis for the decision to
operate a second time. In 2 patients (LJ and GM)
with diagnosed spinal canal stenosis, CT myelography provided more accurate assessment of the
lesions inside the canal and helped in decisions
regarding therapy. In patient PZ, CT myelography
excluded the suspected communication between
the pathologic fluid space in the sacral region and
the dural sac.
Discussion
The methodology of performing and assessment of CT myelography applied in our center
is very similar to that presented by Yamazaki et
al. [16], who used cervical spine puncture from
C1/C2 access in all their patients. In our institution, we applied lumbar puncture as frequently as
suboccipital puncture, thus ensuring diagnostic
contrast of the examined section of the spinal canal in all cases. However, we chose a higher concentration of the contrast medium (300 mg J/ml,
compared to 240 mg J/ml used by the Japanese
authors). Moreover, we performed the study with
a 64-detector device (compared to a 16-detector
device used by Yamazaki et al), which allowed us
to examine a similar section of the spine in a much
shorter time, thus reducing the rate of scans with
artifacts (especially motion artifacts). We used
oblique reconstructions to compensate for cervical lordosis and to obtain symmetric images of
the cord and roots on both sides at the same level.
However, an accurate assessment required several
reconstructions. Yamazaki et al. compensated for
cervical lordosis by positioning the patients’ heads
on a pillow during the scanning and they assessed
ventral roots in the coronal plane and dorsal roots
in oblique scans 20–30º from the coronal plane so
as to obtain an image of dorsal roots on all levels
at one time. Similar to the Japanese authors, we
observed levels with one root – usually the dorsal –
injured, while the ventral root remained intact.
We have observed more injuries in the lower
plexus, which is consistent with the literature and
our previous research [3, 6].
In the cases of roots which had been visible
within pseudocysts – in patients JA and WR, who
were proven during their surgeries to have injured
roots or spinal nerves, it was assumed that the
tear had to be located right outside the pseudocyst
where continuity of the nerve root could not be
traced.
We have noted the presence of lesions within the contours of the spinal cord (patients WR,
RP): deformation of the cord and displacement
toward the injury, raising suspicion of such damage as scars and fibrosis, making it impossible for
the spinal cord to return to the central position in
the dural sac. These displacements were differentiated from compression of the spinal cord by large
pseudocysts located within the canal and displacing the spinal cord contralaterally. Avulsion of the
cord toward the affecting force may lead in rare
cases to bulging of the spinal cord into the pseudocyst, causing severe neurological changes – as in
the case described by Tanaka et al. [17], where
cord herniation into a pseudocyst caused BrownSequard syndrome. A similar case was also reported by Yokota et al. [18].
Penkert et al. [19] compared the results of
MRI and CT myelography with surgical data after laminectomy and intraspinal lesion revision.
In the article by Carvalho [1], assessment of posttraumatic injury of the plexus was also performed
after laminectomy and intradural revision of nerve
structures. In our material, no revision of the spinal canal was performed, and therefore some
roots could be mistaken for normal roots during
the surgery, meaning their continuity was actually
interrupted within the canal while the spinal nerve
in the intervertebral foramen was intact.
Chow et al. [20] reported that the presence of
a pseudocyst itself is not unequivocal evidence of
an avulsion of nerve roots from the spinal cord.
More reliable evidence involves the lack of the
outline of the nerve root in the pseudocyst. We
have confirmed this observation in our previous paper [6] and in the current material, too. In
some cases roots visible against pseudocysts were
not interrupted (OP, CM), while in other cases the
tear was probably located right outside the pseudocyst (JA). Meanwhile, even recently, a pseudocyst was considered virtually the only symptom of
a root tear in CT myelography. The present paper
shows that 64-detector CT myelography with its
potential of producing very thin slices and highquality reconstructions enables direct visualization of nerve roots and a significant improvement
of diagnostic effectiveness in injuries of the brachial plexus.
The authors concluded that 1) 64-detector CT
myelography allows for the efficient assessment of
spinal canal space in patients with contraindications to MRI, 2) application of 64-detector computed tomography allows not only detection of
pseudocysts but also direct assessment of the continuity of particular dorsal and ventral roots, 3) in
the evaluation of CT myelography results, one has
necessarily to consider compression and displacement of the dural sac and spinal cord, which may
lead to significant neurologic sequelae.
Application of 64-Detector CT Myelography
361
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Address for correspondence:
Marek J. Sąsiadek
Department of General and Interventional Radiology and Neuroradiology
Chair of Radiology
Wroclaw Medical University
Borowska 213
50-556 Wrocław
Poland
Tel: +48 71 733 16 60
Received: 11.04.2011
E-mail: [email protected]
Revised: 21.04.2011
Accepted: 2.06.2011
Conflict of interest: None declared