CASE REPO RTS

D o rsa l B r a in

S te m

L ip o m a s : C a s e

R e p o rt

Saleh S. Baeesa, M.B., Ch.B., Michael J. Higgins, M.D.,
Enrique C.G. Ventureyra, M.D.
Division of Neurosurgery, Children's Hospital of Eastern Ontario and University of Ottawa,
Ottawa, Ontario, Canada

INTRACRANIAL LIPOMAS ARE uncommon and rarely symptomatic lesions
accounting for 0.06 to 0.46% of intracranial lesions. The management of
symptomatic dorsal brain stem lipomas was once limited to cerebrospinal
fluid diversion, but with recent advances in microsurgery, they now may be
directly treated. We report three patients with dorsal brain stem lipomas,
twoof which involved the quadrigeminal cistern and one of which was in the
cisterna magna region. Antenatal documentation by ultrasound examination
inone patient represents the first reported in utero diagnosis of quadrigem­
inal cistern lipoma. Computed tomographic and magnetic resonance imaging
scans were diagnostic. The surgical experience in two symptomatic patients
is discussed. Microsurgical decompression was performed in each without
neurological deficit, and clinical symptoms postoperatively subsided. No
patient required a permanent cerebrospinal fluid shunt. The management of
symptomatic dorsal brain stem lipomas is discussed, and an algorithm is
proposed. (Neurosurgery 38:1031-1035, 1996)
fey words: Brain stem, Cisterna magna, Intracranial lipoma, Magnetic resonance imaging,
Quadrigeminal cistern, Ultrasound

In tracran ial l i p o m a s ( I C L s ) a r e u n c o m Im on b en ig n le s io n s o f th e c e n tr a l n e r ­
vous s y s t e m . T h e i r d i a g n o s i s w a s o n c e
lim ited t o i n c i d e n t a l n e c r o p s y f i n d i n g s
" r in freq u en t in c id e n t a l r a d i o g r a p h i c
d iagn osis. R e c e n t a d v a n c e s i n n e u r o i m ­
aging h a v e m a d e a n t e m o r t e m d i a g n o s i s
possible in m a n y p a t i e n t s . A t p o s t m o r ­
te m , V o n d e r a c h e a n d N i e m e r ( 2 7 ) f o u n d
tn u r c a s e s o f I C L a m o n g 5 5 0 0 a u t o p s i e s
10-08% ), w h e r e a s B u d k a ( 2 ) r e p o r t e d
pi n e c a s e s a m o n g 1 9 5 6 s e l e c t e d n e u r o P ath o lo g ical a u t o p s i e s ( 0 . 4 6 % ) . T h e c l i n lcal i n c i d e n c e d e t e c t e d b y c o m p u t e d t o ­
p o g rap h ic ( C T ) s c a n s w a s a l m o s t
e n t i c a l . F a e r b e r a n d W o l p e r t ( 5) r e ported f i v e c a s e s d i a g n o s e d b y C T s c a n
am ong 6 1 2 5 p a tie n ts ( 0 .0 8 % ) . In a la r g e
j^ r i e s , K a z n e r e t a l . ( 12 ) r e p o r t e d 11
^
(0 .0 6 % ) a m o n g 1 7 ,5 0 0 p a t i e n t s
stu d ie d h v f^ T n
.j
u D y c_ I s c a n , a n i n c i d e n c e a m o n g
^ () p a tie n ts w i t h i n t r a c r a n i a l t u m o r s
0 ,3 4 %- M a iu r i e t al. (1 6 ), in 1 9 8 8 , r e ­

v ie w e d 2 0 3 ca se s fro m th e litera tu re
a n d fo u n d th at IC L s w e re m o st c o m ­
m o n l y f o u n d in th e c o r p u s c a llo s u m
(64% ). T h e q u a d rig e m in a l or a m b ie n t
ciste rn s (1 3 % ) a n d th e in fu n d ib u la rc h ia sm a tic reg io n (1 3 % ) w e re th e se c ­
o n d m o s t c o m m o n sites o f o c c u rr e n c e ,
a n d th e c e r e b e llo p o n tin e a n g le (0 .0 6 % )
a n d th e s y lv ia n fissu re (0 .0 3 % ) w e r e th e
th ird a n d fo u rth m o s t c o m m o n , re s p e c ­
t iv e ly (1 6 ). A m o n g l i p o m a s in t h e s e lo ­
ca tio n s, h o w e v e r, cereb ello p o n tin e a n ­
g le lip o m a s w e re th e m o s t s y m p to m a tic
(8 0 % ) a n d ca llo sa l a n d sy lv ia n fissu re
lip o m a s (5 0 % each ) an d q u a d rig e m in a l
o r a m b i e n t c i s t e r n l i p o m a s ( 20% ) w e r e t h e
n e x t m o s t sy m p to m a tic . In fu n d ib u la rc h ia s m a tic le sio n s w e re u su a lly a s y m p
to m a tic. W h e th e r s y m p to m s w e r e related
to th e lip o m a p e r se o r to th e c o e x istin g
c o n g e n i t a l m a l f o r m a t i o n s is n o t c le a r (1 6 ).
D o rsa l b ra in ste m lip o m a s (D B S L s) are
th e se co n d m o st c o m m o n IC L s (1 3 -2 6 % )

Neurosurgery, Vol. 38, No. 5, May 1996

after ca llo sa l lip o m a s a n d u s u a lly a re n o t
a sso cia ted w ith co n g e n ita l m a lfo rm a tio n s
(25, 2 6 , 29).
L ip o m a s a r e r a r e ly s e e n in th e m e ­
d u lla , th e p o n s, th e c h o ro id p le x u s, o r
th e b r a in c o n v e x itie s (2, 3 , 1 0 , 1 2 , 1 6 , 1 9 ) .
IC L s a re k n o w n to a d h e r e to a d ja c e n t
n e u ra l tissu e a n d o fte n e n c a s e th e s u r ­
ro u n d in g cra n ia l n e rv e s a n d b lo o d v e s ­
sels, m a k in g c o m p le te e x c is io n a lm o s t
im p o ssib le w ith o u t p e rm a n e n t b ra in
d a m a g e (3, 7, 10, 16, 17, 2 0 ).
W e rep o rt th e ca ses o f th ree ch ild re n
w ith D B S L s. A n a s y m p to m a tic fe m a le
c h ild w a s d ia g n o s e d in u te r o a s h a v in g
q u a d rig e m in a l ciste rn lip o m a (Q C L )
a n d is still r e c e iv in g c o n s e r v a t i v e f o l­
lo w -u p . T w o ch ild ren w ith s y m p to m ­
a tic lip o m a s o f th e q u a d r ig e m in a l c is­
tern a n d th e cistern a m a g n a , re sp e ctiv e ly ,
u n d e rw e n t m icro su rg ica l d e c o m p re ssio n .
T h e ir p re se n tin g s y m p to m s reso lv ed , a n d
th e h y d r o c e p h a lu s p r e s e n t in o n e h a s
arrested .

CASE REPORTS
Patient 1
A 1 5 -y e a r-o ld fe m a le ch ild p re s e n te d
w ith a lo n g h isto ry o f b ifro n ta l h e a d ­
a ch es, o ccu rrin g sin ce th e a g e o f 7 y ears.
H e r h e a d a c h e s , in itia lly in te rp re te d a s
m ig ra in e , w e re w ell c o n tro lle d w ith
m ild a n a lg e sics for m a n y y ea rs, b u t d u r ­
in g th e start o f p u b e rty , th e y in c re a se d
in f r e q u e n c y a n d in te n s ity a n d b e c a m e
a sso cia ted w ith n a u se a , v o m itin g , a n d
d o u b le v isio n . T h e re su lts o f p h y sic a l
a n d n eu ro lo g ica l e x a m in a tio n s w e re n o r­
m a l. A s a n o u tp a tie n t, s h e u n d e r w e n t a
C T scan , w h ich rev ea led a 15 X 2 0 -m m
h y p o d e n s e le s io n in th e q u a d r i g e m i n a l
cistern th at d id n o t e n h a n c e a fte r c o n tra st
in je c tio n a n d a m ild tr iv e n tric u la r d ila ta ­
tio n s u g g e s tiv e o f o b s tr u c tiv e h y d r o c e p h ­
alu s. M a g n e tic r e s o n a n c e (M R ) im a g e s
(Fig. I A) r e v e a l e d a 1 5 X 1 5 X 2 0 - m m
h o m o g e n e o u s le s io n in th e left q u a d r i ­
g e m in a l p la te c o m p r e s s i n g th e left c o llicu li w it h o u t d e fin ite a q u e d u c t a l o b s t r u c ­
tio n . T h e le s io n w a s h y p e r in te n s e o n
T l-w e ig h te d im a g e s an d h y p o in ten se o n
T 2- w e i g h t e d i m a g e s . T h e r e w a s n o e n ­
h a n c e m e n t w ith g a d o lin iu m -d ie th y le n e

1031

1032

B a e e s a e t a l.

F IG U R E 1. Patient 1. A, sagittal M R
T1 -w eigh ted im age d e m o n stratin g a 15
x 2 0 -m m Q C L co m p re ssin g the c o llic u ­
lar plate and the ce re b ra l a q u e d u ct.
Th e third v e n tricle is e n large d . Bf p o st­
operative sagittal M R T 1 -w e ig h te d
im age sh o w in g an u n ch a n g e d lip o m a
rem nant after subtotal e x cisio n o v e r 5
years of fo llo w -u p .

tria m in e p e n ta -a c e tic a cid a d m in is tra tio n .
B ra in ste m a u d ito ry e v o k e d re s p o n s e s
(B A E R s ) w e r e slig h tly p ro lo n g e d , m a in ly
o n th e left sid e . S o m a t o s e n s o r y e v o k e d
p o ten tia ls (S S E P s) w e r e w ith in n o rm a l
lim its. In J a n u a r y 1 9 9 0 , th r o u g h a left o c ­
cip ital tra n ste n to ria l a p p r o a c h , a y e llo w
e n c a p s u la te d lesio n , w h ic h p r o v e d to b e
a d h e re n t to th e s u p e rio r co llicu lu s, w a s
su b to ta lly ex cised . T h e lip o m a w a s n o t
a d h e r e n t to th e left tr o c h le a r n e r v e o r th e
s u p e rio r c e re b e lla r a rteries. C o m p le te e x ­
cisio n w a s th e n c o n s id e re d to b e im p o s s i­
b le w ith o u t irrev ersib le n e u ro lo g ic a l in ­
ju ry . N o s h u n t w a s r e q u ir e d . A r ig h t
h o m o n y m o u s h e m ia n o p sia w a s d etected
d u rin g th e ea rly p o sto p e ra tiv e p erio d . A
p o sto p era tiv e C T scan at 2 w e e k s sh o w e d
resid u al lip o m a b u t n o p ro g re ssio n o f th e
h y d ro ce p h a lu s. H isto lo g ica l e x a m in a tio n
c o n firm e d th e ra d io lo g ica l a n d su rg ica l
d ia g n o sis o f lip o m a . T h e p a tien t w a s d is­
ch a rg e d o n th e 15th p o sto p e ra tiv e d a y
w ith n o r m a l B A E R s . H e r v is u a l field d e ­
fect c o m p le te ly re c o v e re d a fte r 4 w e e k s ,
a n d sh e h a s sin ce re m a in e d n e u ro lo g i­
c a l l y i n t a c t . M R i m a g i n g (Fig. IB) s h o w e d
n o c h a n g e in t h e s iz e o f t h e r e s id u a l li­
p o m a o r in th e v e n tr ic u la r s iz e o v e r a
5 -y e a r p erio d .

Patient 2
A 1 4 -y ea r-o ld fe m a le p a tien t p re ­
sen ted w ith a h isto ry o f p ro g re ssiv e o c ­
cip ita l h e a d a c h e , u n s te a d in e s s , n a u s e a
a n d v o m itin g , a n d b lu rre d v isio n , w h ic h
h a d c o n tin u e d for se v e ra l w e e k s. P h y s ­
ical e x a m in a t io n r e v e a le d a so ft, n o n ­
ten d er m id ce rv ica l m a ss. N e u ro lo g ica l
e x a m in a tio n
rev ea led
m ild
tru n cal

F IG U R E 2. Patient 2. A, sagittal M R
T 1 -w e ig h te d im age re v e a lin g a 6 5 x
4 5 -m m ciste rn a m agn a lip o m a e n c a s in g
and co m p re ssin g the in fe rio r pons and
m e d u lla w ith e xte n sio n th ro u g h the
fo ram e n m a gn u m . B, p o sto p e ra tive sa g ­
ittal M R T 1 -w e ig h te d im age d e m o n ­
stratin g residual lip o m a after m ic r o s u r ­
g ica l d e co m p re ssio n . T h e lip o m a has
not ch a n g e d o v e r 5 years o f fo llo w -u p .

a ta x ia a n d d o w n b e a tin g n y s ta g m u s . A
C T sca n s h o w e d a la rg e e x tra -a x ia l le­
sio n in th e c iste rn a m a g n a re g io n , w h ic h
a p p e a re d to b e h y p o d e n s e a n d d id n o t
e n h a n c e after co n tra st a d m in istra tio n .
T h e re w a s n o a sso cia te d h y d ro c e p h a lu s.
T h e su b cu tan eo u s m ass m easu red 35 X
3 0 m m a n d a p p e a r e d to b e o f th e s a m e
ra d io lo g ica l d e n sity as th e in tra cra n ia l
lesio n . A s p in a b ifid a o f th e C l v e rte b ra
w a s seen o n b o n e w in d o w s . S a g itta l T lw e i g h t e d M R i m a g e s (Fig. 2A) s h o w e d a
65 X 45 X 4 0 -m m h o m o g e n e o u s h ig h
sig n a l in te n sity le sio n e x te n d in g fro m
th e fo u rth v e n tric le to th e le v e l o f th e C l
v erteb ra, co m p re ssin g th e m e d u lla a n d
a n terio rly d isp la cin g th e c e rv ic o m e d u l­
la ry ju n c tio n . T h is le s io n w a s h y p o in ­
ten se o n T 2 -w e ig h te d im a g es. T h e re
w a s n o a n a to m ic rela tio n sh ip b e tw e e n
th e s u b c u ta n e o u s a n d th e in tra cra n ia l
lesio n s. B A E R s a n d S S E P s w e r e s ig n ifi­
ca n tly b ila tera lly d e la y e d . S u rg ica l re ­
s e c tio n w a s p e r f o r m e d in J u ly 1 9 9 0
th ro u g h a m id lin e su b o ccip ita l c ra n ie c ­
to m y w ith C l la m in e c to m y a n d in itia lly
co n siste d o f p a rtia l e x cisio n o f th e
su b c u ta n e o u s lip o m a . T h e d u ra w a s
slig h tly te n se a n d , o n c e o p e n e d , re ­
v e a le d a la rg e y e llo w c a p su la te d tu m o r
en v elo p ed b y a ra ch n o id m e m b ra n e c o n ­
ta in in g p r o m in e n t b lo o d v essels. S u b to ­
tal m ic r o s u r g ic a l r e s e c t io n w a s p e r ­
fo rm e d w ith th e u se o f an u ltra so n ic
a sp ira to r w ith c o n c u rre n t sh rin k a g e u s ­
in g b ip o la r c o a g u la tio n . T h e tu m o r e n ­
c a s e d th e left lo w e r c r a n ia l n e r v e s (IX th ,
X th , a n d X lth cra n ia l n e rv e s) a n d th e
p o ste rio r in fe rio r c e re b e lla r a rteries,

Neurosurgery, Vol. 38, No. 5, May 19 96

w h i c h w e r e l e f t i n t a c t w i t h o u t in ju ry . A
p o r t i o n o f t h e t u m o r t i g h t l y a d h e r e n t to
t h e f l o o r o f t h e f o u r t h v e n t r i c l e was l e f t
u n d i s t u r b e d . B e c a u s e t h i s m a s s was te­
n a c i o u s l y a d h e r e n t t o t h e m e d u lla ob­
l o n g a t a a n d l o w e r c r a n i a l n e r v e s , rad i­
c a l e x c i s i o n w a s c o n s i d e r e d to be
h a z a r d o u s . S u b s e q u e n t w a t e r t i g h t dural
c l o s u r e r e q u i r e d a c a d a v e r i c d u r a l graft.
T h e p o s t o p e r a t i v e c o u r s e o f t h e patient
w a s u n e v e n t f u l , a n d s h e w a s d isch arged
o n t h e 8t h p o s t o p e r a t i v e d a y a fte r
r e m a r k a b l e i m p r o v e m e n t o f h e r preoper­
a t i v e n e u r o l o g i c a l s y m p t o m s . H istologi­
c a l e x a m i n a t i o n c o n f i r m e d t h e d iagn osis
o f l i p o m a . P o s t o p e r a t i v e S S E P s and
B A E R s b e c a m e n o r m a l . S e r i a l M R im ag­
i n g (Fig. 2B) s h o w e d a s t a b l e l i p o m a r e m ­
n a n t d u r i n g 5 y e a r s o f s y m p t o m - f r e e fol­
lo w -u p .
I

Patient 3
D u r i n g r o u t i n e p r e n a t a l u ltraso u n d
a t 3 6 w e e k s g e s t a t i o n , a d o r s a l brain
s t e m m a s s w a s i d e n t i f i e d in a n other­
w i s e n o r m a l f e t u s (Fig. 3, A a n d B). T h e
p r e g n a n c y c o n t i n u e d t o t e r m w ith o u t
i n c i d e n t , a n d a t b ir t h , th is fe m a le baby
w a s n o r m a l . C r a n i a l u l t r a s o u n d o n the
2n d d a y o f l i f e d e m o n s t r a t e d a q u a d r i ­
g e m i n a l c i s t e r n m a s s s u g g e s t i v e o f li­
p o m a (Fig. 3 , C a n d D ) . H e r h e a d c ir ­
c u m f e r e n c e w a s 3 7 c m ( 7 5 t h p ercen tile
f o r a g e ) . T h e a n t e r i o r f o n t a n e l w a s s o ft
a n d s u n k e n i n e r e c t p o s i t i o n . S h e was
n e u r o l o g i c a l l y in t a c t . A C T s c a n show ed
a h y p o d e n s e n o n e n h a n c i n g 1 0 X 12-m m
l e s i o n in t h e q u a d r i g e m i n a l cistern . M R
i m a g i n g (Fig. 3 , E a n d F ) s h o w e d a 1 4 X
1 0 X 1 0 - m m l e s i o n ( h v p e r i n t e n s e T la n d h y p o i n t e n s e T 2 - w e i g h t e d im ages),
w h i c h f i l l e d t h e q u a d r i g e m i n a l cistern
a t t h e le f t s u p e r i o r c o l l i c u l u s a n d pro­
d u c e d m i l d f o c a l c o m p r e s s i o n o f th e
m i d b r a i n w i t h o u t o b s t r u c t i o n o f cere­
b r o s p i n a l f l u i d p a t h w a y s , co n sisten t
w i t h l i p o m a . S S E P s a n d B A E R s w ere
n o r m a l . D u r i n g c l i n i c a l f o l l o w - u p and
a n n u a l M R i m a g i n g (Fig. 3, E a n d F)
o v e r 3 y e a r s , t h is c h ild r e m a in e d neuro­
l o g i c a l l y i n t a c t a n d h e r l i p o m a re­
m a i n e d a s y m p t o m a t i c d e s p i t e a d efin ite
in c r e a s e in siz e .

D ISCU SSIO N
I C L s a r e b e n i g n l e s i o n s , neither
h a m a r t o m a s n o r t r u e n e o p l a s m s ; rather,

Dorsal Brain Stem Lipomas

FIGURE 3. Patient 3. T ra n sa b d o m in a l
axial (4) and coronal ( B) s o n o g ra p h ic
images of the fetal head, d e m o n stra tin g
an 8-mm dorsal brain stem h y p e re c h o ic
mass. Sagittal ( C ) and a xia l (D) n e o n a ­
tal ultrasound im ages c o n firm a h y p e r­
echoic 8 x 10-m m m ass near the te n to ­
rial incisura suggestive o f D B S L . Sagittal
(Eland axial ( F ) M R T 1 -w e ig h te d
images obtained at age 3 years, d e m o n ­
strating a 12 x 14-m m Q C L ; a c o m p a r ­
ison with postnatal M R im ages d e m o n ­
strates that the mass has e n la rg e d .

[h e y a r e c o n g e n i t a l m a l f o r m a t i o n s a n d
tend t o a r i s e n e a r t h e m i d l i n e ( 2 , 12 , 1 6 ,
17, 2 5 ) . N u m e r o u s p a t h o g e n i c t h e o r i e s
have b e e n d e s c r i b e d , i n c l u d i n g t h e f o l ­
d i n g : 1) h y p e r t r o p h y o f p r e e x i s t i n g
m e n in g e a l f a t t y t i s s u e ; 2) o r i g i n f r o m
' 't h i n t h e b r a i n s u b s t a n c e , l i p o m a t o u s
gliom a; 3 ) t r a n s f o r m a t i o n o r m e t a p l a s i a
°t m e n i n g e a l c o n n e c t i v e t i s s u e ; 4 ) f a t t y
g e n e r a t i o n o f p r o l i f e r a t e d g l i a ; 5) m e M>d e r m a l i n c l u s i o n w i t h i n t h e l i p s o f t h e
*( ) s m g n e u r a l t u b e ( d y s r a p h i s m t h e o 7 ) / a n d 6) d e r i v a t i o n f r o m t h e e m b r y o °gical " m e n i n x p r i m i t i v a , " a m e s e n ­
chym al d e r i v a t i v e o f n e u r a l c r e s t ( 2 5 ) .
he f i n a l t h e o r y h a s i n v a l i d a t e d p r e v i ) ls P a t h o g e n i c t h e o r i e s , s u g g e s t i n g a n
n°rm a l, p e r s is t e n t f o c u s o f m e n i n x
P fin h tiva d i f f e r e n t i a t i o n i n t o a d i p o s e
lssue a n d m a t u r a t i o n i n t o a l i p o m a . It
j ! ? P ly e x p l a i n s t h e c i s t e r n a l l o c a t i o n o f
S'
in h * a le s io n a l l o c a t i o n o n b l o o d
( s s e l s ar|d c r a n i a l n e r v e s , a n d t h e a b ­

se n c e o f o th e r m e s o d e r m a l d e riv a tiv e s,
s u c h a s m u s c le a n d ca rtila g e. H o w e v e r ,
it d o e s n o t f u l l y e x p l a i n t h e c o m m o n
a sso cia tio n o f co n g e n ita l m a lfo rm a tio n s
w ith ca llo sa l lip o m a s. T h e n a tu ra l h is­
t o r y o f t h e s e le s io n s is u n k n o w n , b u t
th e y m a y e n la r g e w ith tim e . In th e p o s ­
te r io r fo s s a , t h e y o c c u r e ith e r in th e d o r ­
sal m id lin e , v e n tra l to th e b ra in s te m , o r
in th e c e r e b e llo p o n tin e a n g le .
D B S L s in c lu d e th o s e r e s id in g in th e
q u a d r i g e m i n a l o r a m b i e n t c is te r n s , in
th e su p e rio r v e rm is an d su p e rio r m e d ­
u lla r y v e lu m , a n d in th e c is te r n a m a g n a
o v e r th e m e d u lla o b lo n g a ta . V en tra l
b r a in s t e m lip o m a s a n d th o s e a r is in g in
th e u p p e r cerv ica l sp in a l co rd e x te n d in g
to th e p o s te rio r fo ssa (18, 25, 28) a re n o t
in clu d e d h ere. A m o n g n u m e ro u s IC L s,
m o r e th a n 6 0 le s io n s a r o s e in th e d o r s a l
b r a in s te m (1 -3 , 5 -1 7 , 1 9 -2 7 , 29, 30).
O n ly th r e e lip o m a s w e r e fo u n d in th e
cistern a m a g n a , in clu d in g o n e a u to p sy
fin d in g , o n e in cid e n ta l C T sca n fin d in g ,
a n d o n e , w h ic h p ro d u ce d n e ck p a in an d
tru n ca l a ta x ia , treated su cce ssfu lly w ith
s u b to ta l r e s e c tio n (2, 3, 16). T h e r e m a in ­
in g le sio n s w e re p re d o m in a n tly lo ca ted
in th e q u a d r ig e m in a l r e g io n . T h e d ia g ­
n o s i s w a s e s t a b l i s h e d b y n e c r o p s y i n 21
p a t ie n t s a n d a fte r n e u r o i m a g i n g in th e
rest. In c o n tr a s t to s u p r a te n to ria l lip o ­
m a s, m a n y rep o rted D B S L s w e re s y m p ­
to m a tic , e ith e r b e c a u se o f d irect b ra in
s te m a n d cere b ella r c o m p re ssio n o r d is­
t o r t i o n o f t h e c e r e b r a l a q u e d u c t ( 3 , 6, 7 ,
9, 1 1 , 12 , 1 6 , 1 7 , 2 1 , 2 4 , 2 6 ) . D B S L s p r o ­
d u c in g d irect b ra in ste m o r ce re b ella r
c o m p r e s s io n clin ica lly p re se n t as focal
m a s s le sio n s w ith o cu la r a p ra x ia , d ip lo ­
p ia , h e m ia n e s th e s ia , a ta x ia , a n d / o r
h e a d a c h e (3, 12, 16, 2 1 , 2 6 ). L ip o m a s
d istu rb in g th e flo w o f ce re b ro sp in a l
flu id th r o u g h th e c e re b ra l a q u e d u c t p r o ­
d u c e s y m p to m s o f in crea sed in tra cra ­
n ia l p r e s s u r e s e c o n d a r y to o b s tr u c tiv e
h y d r o c e p h a l u s ( 1 , 6, 7 , 9 , 1 1 , 1 2 , 1 7 ) .
O cca sio n a lly , D B S L s p resen t co in cid e n t
to s e iz u r e d iso rd e rs, d e m e n tia , a n d
m e n ta l reta rd a tio n , su g g e stin g th ey
m a y b e e p ip h e n o m e n a o f a co ex ist
in g c o n g e n ita l m a lf o r m a tio n (9, 13, 16,
2 5 , 26).
T h e C T an d M R im a g in g scan ch a ra c­
teristics o f D B S L s a re p a th o g n o m o n ic
a n d a llo w a co n fid e n t d ia g n o sis w ith o u t
b io p s y co n firm a tio n . O n C T sca n s, lip o ­
m a s a re h y p o d e n s e sh a rp ly d e m a rca te d

Neurosurgery, Vol. 38, No. 5 , May 996
1

1055

lesio n s w ith a tte n u a tio n v a lu e s o f — 5 0
to - 1 0 0 H o u n s fie ld u n its, la c k c o n tr a s t
e n h a n c e m e n t, an d m a y h a v e o cca sio n a l
r i m c a l c i f i c a t i o n s ( 6, 1 2 , 1 5 ) . O n M R i m ­
a g in g , IC L s sh o rte n T l a n d T 2 rela x ­
a tio n tim e s, th u s y ie ld in g h y p e rin te n s e
h o m o g e n e o u s s ig n a l in T l - w e i g h t e d i m ­
a g e s a n d h y p o in t e n s e s ig n a l in T 2 w e i g h t e d i m a g e s ( 6, 2 5 , 2 6 ) . A t t e n t i o n t o
p re c ise n e u r o im a g in g criteria a llo w s
d ifferen tia tio n o f IC L s fro m o th e r m a ss
lesio n s. D e r m o id a n d e p id e r m o id cy sts
h a v e h ig h e r a tte n u a tio n v a lu e s a n d
a re less h o m o g e n e o u s . T e r a to m a s a re
h e te ro g e n e o u s lesio n s th at m a y e n ­
h a n c e w ith co n trast. M y e lo lip o m a s a n d
a n g io lip o m a s ty p ica lly s h o w in te n se e n ­
h a n c e m e n t after co n tra st a d m in is tra ­
tio n . IC L s , h is to lo g ic a lly , a r e w e llcircu m scrib e d m a sse s su rro u n d e d b y
a th in fib ro u s c a p s u le a n d , c la ssica lly ,
a re c o m p o s e d o f m a tu r e a d ip o s e ce lls
s e p a ra te d b y th in , d e lic a te fib ro u s
s e p ta (3).
T h e an ten atal d ia g n o se s o f a Q C L
(P a tie n t 3), a p o n tin e lip o m a (2 9 ), a n d
th r e e lip o m a s o f th e c o r p u s c a llo s u m (4,
19) stro n g ly su p p o rt th e c o n c e p t th at
IC L s a re c o n g e n ita l le sio n s. C o n tr o v e r s y
re g a rd in g th e n a tu ra l h isto ry o f IC L s
p ersists, in c lu d in g w h e th e r, at w h a t
ra te , a n d in w h ic h p a tie n ts th e y g r o w .
T h e rela tiv ely h ig h in c id e n c e o f s y m p ­
to m a tic n e u r a l c o m p r e s s io n in D B S L s ,
e s p e c ia lly in a d o le s c e n t s a n d a d u lts ,
su g g e sts th at s o m e lip o m a s in d e e d
g ro w . A d d itio n a l e v id e n ce fro m o u r p a ­
tie n ts s u p p o r ts th is h y p o th e s is . P r o g r e s ­
siv e s y m p to m s o v e r a lo n g in te rv a l, as
in o u r first a d o le s c e n t p a tie n t, o r th e
a cu te d e v e lo p m e n t o f sig n ifica n t s y m p ­
t o m s a n d s ig n s in a p r e v io u s ly a s y m p ­
t o m a t ic p a tie n t, a s in o u r s e c o n d a d o l e s ­
ce n t p a tien t, in d ire ctly s u g g e s t th a t IC L s
d o g ro w . F u rth e rm o re , th e d o c u m e n ta ­
tio n o f n e u r o p h y s io lo g ic a l a b n o r m a li­
ties a n d th e p r o m p t r e s o lu tio n o f b o th
th e clin ica l a n d n e u r o p h y s io lo g ic a l a b ­
n o r m a lit ie s in e a c h o f o u r p a t ie n t s a fte r
d e c o m p re ss io n a rg u e th at th ese D B S L s
h ad in d eed b e c o m e p a th o lo g ica l. O u r
y o u n g p a tien t (P a tien t 3) h a s s h o w n d e f­
in ite lip o m a g r o w th b u t, a s y e t, h a s d e ­
v e lo p e d n o clin ica l s y m p to m s . U n fo r tu ­
n a t e ly , n o I C L s p r e v i o u s l y r e p o r t e d in
th e lite ra tu re h a v e b e e n s h o w n to in ­
c r e a s e in s iz e o r p r o d u c e p r o g r e s s iv e
s y m p to m s after d ia g n o sis o r treat-

1034

B a e e s a e t a l.

TABLE 1. Surgical Experience with Dorsal Brain Stem Lipomas
Surgery

Symptoms/Signs

Size (mm)

Series (Ref. No.)

Age/Sex

Location

K a z n e r e t a l.,

36 y r / F

17X11

H eadache

E x cisio n

Im proved

M ed iu m

H y d ro cep h a lu s

VPS

Im proved

6 2 yr/M

Q u a d rig em in a l
cistern
S u p erio r m e d u lla ry
v elu m
A m b ie n t cistern

Large

B io p sy , V P S

Im proved

73 y r / M

C istern a m a g n a

50 X 40 X

30

D e co m p re ssio n

Im proved

65 y r / M

Q u a d rig em in a l
cistern
Q u a d rig em in a l
cistern
S u p erio r v erm is

33 X

30

H e a d a c h e , d ip lo p ia ,
h y d ro cep h a lu s
N u ch a l so ren ess, tru n cal
a ta x ia
A b d u c e n s n e rv e p a lsy

E x cisio n

Im proved

S m all

H y d ro cep h a lu s

VPS

Im proved

4 0 X 3 0 X 25

O c u la r m o to r a p ra x ia

E x cisio n

Unchanged

1 2 X 1 0 X 9

T e n s e a n terio r fo n ta n e le ,
h y d ro ce p h a lu s
N /V, h e a d a c h e , b lu rred
v isio n
O ccip ita l h e a d a ch e ,
N/V, a ta x ia , n y sta g m u s

VPS

Im proved

D e co m p re ssio n

Im proved

D e co m p re ssio n

Im proved

1 9 8 0 (12)

F r ie d m a n e t a l.,

6 3 yr/M

1 9 8 6 (6)

M a iu r i e t a l.,
1 9 8 7 (16)

C h o e t a l.,
1991 (3)

N ik a d io e t a l.,
1 9 9 3 (21)

H a y a s h i e t a l.,

3 d/M

1 9 8 3 (9)

S u m m e r s e t a l.,

10 m o / F

30 X

O utcom e

1 9 8 7 (24)

K a w a m a t a e t a l.,

1 d/M

1 9 9 5 (11)

T h is stu d y,
P a tien t 1
T h is stu d y,
P a tien t 2

15 y r/ F
14 y r / F

Q u a d rig em in a l
cistern
Q u a d rig em in a l
cistern
C istern a m a g n a

15 X

15 X 2 0

65 X 45 X 4 0

N/V, nausea and vomiting; VPS, ventriculoperitoneal shunt.

m en t. A n e stim a te o f th e tru e n atu ral
h isto ry o f IC L s m a y b e d e d u c e d fro m
fu rth er o b se rv a tio n o f o u r y o u n g p a ­
tie n t a n d o th e rs lik e h e r o r, p e r h a p s ,
fro m n e w rep o rts d e ta ilin g th e lo n g ­
term o u tco m e s o f p re v io u sly rep o rted
p a tie n ts.
S u rg ica l tre a tm e n t o f D B S L s h as
b e e n r e p o r t e d i n 10 p a t i e n t s , i n c l u d i n g
th e tw o p a tie n ts d e scrib e d h erein (see
Tabic 1). T h e t w o c i s t e r n a m a g n a l i p o ­
m a s h a d id e n tica l clin ica l p r e s e n ta ­
tio n s, a n d e a c h w a s s u b to ta lly re ­
m o v e d th ro u g h m id lin e su b o ccip ita l
a p p ro a c h e s w ith g o o d o u tc o m e . Q C L s
in fo u r p a tie n ts w h o e a c h p r e s e n te d
w ith s y m p to m s re la te d to o b s tr u c tiv e
h y d ro c e p h a lu s w e re treated b y in se r­
tio n o f v e n tr ic u lo p e r ito n e a l s h u n ts .
D ire ct su rg ica l tre a tm e n t o f Q C L s w a s
p e r f o r m e d in fo u r p a t ie n t s ( th r e e to ta l
re m o v a ls a n d o n e su b to tal rem o v a l).
T h e p re se n tin g n eu ro lo g ica l s y m p ­
to m s im p r o v e d o r r e s o lv e d in a ll e x ­
cep t o n e w h o rem a in e d u n ch a n g e d .
W e , l i k e K a w a m a t a e t a l. ( 11), t h i n k
t h a t t h e s i z e o f s y m p t o m a t i c Q C L s is
n o t a lim it in g f a c t o r in t r e a t m e n t p l a n ­
n in g . In e x p e r ie n c e d h a n d s , w ith m i­
cro su rg ica l la se r-a ssisted te c h n iq u e s
an d a C a v itro n u ltra so n ic a sp ira to r,
d ir e c t s u r g ic a l t r e a t m e n t o f D B S L s is

s a f e a n d s y m p t o m a t i c i m p r o v e m e n t is
th e lik e ly o u tc o m e . W e fo u n d S S E P s
a n d B A E R s h e lp fu l in p re - a n d p o s t­
o p e ra tiv e a sse ssm e n t. In tra o p e ra tiv e
B A E R (18) a n d S S E P m o n ito r in g m a y
b e o f b e n e fit. T h e g o a l o f s u rg e ry
sh o u ld b e a d e q u a te d e c o m p re s s io n ,
b e c a u se th e se le sio n s a re te n a c io u sly
a d h e r e n t to u n d e r ly in g n e u ra l tissu e ,
cra n ia l n e rv e s, a n d s u r r o u n d in g v e s ­
sels. R a d ic a l e x c is io n o ffe r s little a d d i­
tio n a l b e n e fit b u t m a y g re a tly in c re a s e
th e ris k o f b r a in in ju ry . N e u r o e n d o ­
sc o p ic th ird v e n tr ic u lo s to m y m a y b e a
r e a s o n a b le a lte rn a tiv e to th e v e n tr ic u ­
lo p e r ito n e a l s h u n t in t h o s e p a t ie n t s
w h o s e s y m p to m s a n d sig n s so le ly re ­
la te to o b s tr u c tiv e h y d r o c e p h a lu s . T h e
p re se n c e o f focal sig n s o r d e ficits re ­
la te d to b ra in s te m c o m p r e s s io n in d i­
c a te th a t s im p le c e re b ro s p in a l flu id d i­
v e r s io n w ill p r o v e to b e in a d e q u a te
tre a tm e n t for s y m p to m a tic D B S L s. P a ­
tie n ts p re s e n tin g fo cal sig n s o r e v i­
d e n c e o f sig n ifica n t b ra in ste m c o m ­
p re ssio n sh o u ld b e c a n d id a te s for
m ic ro s u rg ic a l d e c o m p r e s s io n . In c o n ­
clu sio n , w e p ro p o s e an a lg o rith m fo r
t h e m a n a g e m e n t o f D B S L s (Fig, 4 ) , i n ­
co rp o ra tin g th e p rin cip le s d iscu sse d
above.

Neurosurgery, Vol. 38, No. 5, May 1996

D BSLs

CT /MR /BA ER /SSEP

Observe

Hydrocephalus

BrainstemCompression
(+/- hydrocephalus)
BAER SSEP

VPS or V d Ventriculostom y

Surgical Decom
pression

F IG U R E 4. M anagem ent algorithm ot
D B SLs.

ACKNOW LEDGM ENTS
W e t h a n k D r . H e a t h e r B r a y t o r rt
v i e w i n g t h e p r e n a t a l u l t r a s o u n d . Librai
i a n s R o s e - M a r i e M o n g e o n , P a t Johnsor
a n d P a m L e m o i n e a s s i s t e d w i t h t h e lil
e ra tu re rev iew .
Received, November 13, 1995.
Accepted, December 4, 1995.
Reprint requests: E.C.G. V e n t u r e y r a , MDivision of Neurosurgery, C h ild re n s Ho^
tal of Eastern Ontario, 401 Smyth R o a d
tawa, Ontario K1H 8L1, Canada.

D o r s a l B r a in S te m L ip o m a s
19. Mulligan G , Meier P: Lipoma and agenesis of

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1 0 3 5

fo rm a tio n a sso cia te d w ith a clo sed n e u ­
ra l t u b e d e f e c t a n a l o g o u s to w h a t is u s u ­
a lly s e e n in th e lu m b o s a c r a l r e g io n .
O p e ra tiv e in te rv e n tio n w a s in d ica ted
a n d s u c c e s s fu l in th is p a tie n t. In th e
th ird p a tie n t, th e m a s s w a s n o te d a s a n
in cid e n ta l fin d in g o n fetal u ltra s o n o g ra ­
p h y . T h is p a tien t h a s receiv ed fo llo w -u p
for 3 y e a rs w ith o u t a n y n o tice a b le
c h a n g e in th e s iz e o f th e m a s s e x c e p t fo r
p ro p o rtio n a l g ro w th w ith th e b ra in . T h e
au th o rs a p p ro p ria tely h a v e n o t o p e r­
a te d o n th is p a tie n t, a s th e m a s s is n o t
o b s tru c tin g c e re b ro s p in a l flu id flo w a n d
h a s n o t p r o d u c e d a n e u r o lo g ic a l d eficit.
T h e m a jo rity o f in tra c ra n ia l lip o m a ­
to u s m a s s e s s im ila r to th e o n e s d e ­
scrib ed b y th e a u th o rs a re in cid e n ta l
fin d in g s o n im a g in g stu d ie s a n d d o n o t
req u ire o p e ra tiv e in terv en tio n . F o l­
lo w -u p w o u ld co n sist o f m a g n e tic re so ­
n a n ce stu d ies at p ro g re ssiv e ly in cre a s­
in g in terv a ls. T h e n e e d fo r d o in g a n y
a d d itio n a l stu d ies, su ch as c o m p u te d to ­
m o g ra p h y , b ra in ste m a u d ito ry e v o k e d
resp onses, an d so m ato sen so ry ev ok ed
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T h i s is a t h o u g h t f u l r e v i e w o f a v e r y
r a r e p a t h o lo g ic a l e n tity in th r e e p a ­
tie n ts, tw o o f w h o m s e e m to h a v e b e e n
s y m p t o m a t i c . In m y e x p e r i e n c e , th is is
r a re ly th e c a s e a n d th e m a jo rity o f th e se
m a s s e s a re e sse n tia lly h a m a rto m a s w ith
n o tru e clin ica l sig n ifica n ce . N e v e r th e ­
less, th e a u th o rs p re se n t a v e ry c o m p le te
r e v ie w o f th e lite ra tu re a n d tw o v e ry
w e ll-illu s tr a te d c a s e s in w h ic h th e p a ­
tie n ts s e e m to h a v e b e n e fite d fro m s u r ­
g ica l e x cisio n .
L u is S c h u t
Philadelphia, Pennsylvania

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T h e a u th o rs rep o rt th ree p a tie n ts
w ith p o ste rio r fossa lip o m a to u s m asses.
I w o n d e r w h e th e r th e o u tc o m e o f th e
first p a tie n t m ig h t h a v e b e e n th e s a m e ,
irre sp e ctiv e o f o p e ra tiv e in te rv e n tio n .
T h e s e c o n d p a tie n t s e e m e d to h a v e a

64 :9 7 4 -9 7 6 , 1 9 8 6 .

Neurosurgery , Vol. 38, No. 5, May 1996

T ectal lip o m a s can b e co m p le te ly
a s y m p to m a tic o r th e y c a n g iv e rise to
h y d r o c e p h a lu s , a s in P a t ie n t 1. I t h in k
th at th e p re fe rre d m e th o d o f tre a tm e n t
is a t h ir d v e n t r i c u l o s t o m y o r a d i v e r ­
s io n a r y s h u n t ra th e r th a n a n a tte m p t to
re m o v e th e lip o m a .
P a tien ts w ith lip o m a s at th e c ra n io c e r­
v ica l ju n c tio n c a n p re s e n t w ith sig n ific a n t
n e u ro lo g ic a l d eficits. 1 h a v e h a d th re e p a ­
tie n ts w it h th e s e , all o f w h o m p r e s e n t e d
w ith sig n ifica n t w e a k n e s s o f th eir e x tr e m ­
ities b e c a u s e o f c o m p r e s s io n o f c e r v ic a l
co rd . S o m e o f th ese in tra m e d u lla ry lip o ­
m a s a t th e c ra n io c e r v ic a l ju n c tio n w ill
h av e su b cu tan eo u s m asses, w h ereas o th ­
e rs w ill h a v e n o c u ta n e o u s s ig n s w h a ts o ­
ev er. T h e s e p a rticu la r lip o m a s req u ire
su rg ica l d e b u lk in g , b e c a u s e th e y d o p r o ­
d u c e sig n ific a n t d eficits.
H a r o ld J. H o f f m a n
Toronto, Ontario, Canada