Cervical spinal arachnoid cyst in a dog
Cary T. Hashizume
Abstract-An 18-month-old, intact male Akita presented with a 12-month history of progressive
ataxia, hypermetria, and loss of conscious proprioception of the thoracic and pelvic limbs.
Neurological examination and myelography localized a lesion at cervical vertebrae 1 and 2 consistent
with an arachnoid cyst. Hemilaminectomy and cyst fenestration led to virtually full recovery.
Resume-Kyste cervico-spinal de I'arachnoide chez un chien. Un Akita male entier de 18 mois
a ete presente pour une histoire d'ataxie progressive, d'hypermetrie et de perte de sensibilite
proprioceptive des membres thoraciques et pelviens, le tout s'etendant sur une periode de 12 mois.
L'examen neurologique et la myelographie ont localise une lesion au niveau des vertebres cervicales
1 et 2, compatible avec un kyste arachnoYdien. L'hemilaminectomie et la fenestration du kyste ont
conduit a guerison quasi-complete.
(Traduitpar docteur Andre Blouin)
Can Vet J 2000;41:225-227
An 18-month-old, intact male Akita was presented to
tAtthe Western College of Veterinary Medicine
Veterinary Teaching Hospital (WCVM-VTH) with a
12-month history of progressive ataxia, hypermetria, and
loss of conscious proprioception of the thoracic and
pelvic limbs. His previous medical history was unre-
markable, and there was no history of trauma.
Physical examination revealed a dog that was bright,
alert, and responsive, with abnormalities confined to the
nervous system. He had a base-wide stance with quadri-
lateral ataxia and knuckling of the digits of the tho-
racic and pelvic limbs. Significant dorsal scuffing of the
nails of the 3rd and 4th digits of the thoracic limbs
was noted. Moderate pelvic limb hypermetria and
marked thoracic limb hypermetria were noted at a walk
and became more severe at a trot. Knuckling responses
were slow in the left thoracic limb and left pelvic limb.
Spinal reflexes were normal, except for the patellar
tendon reflexes, which were hyperreflexive bilaterally.
Mentation and cranial nerve function were normal.
Pain could not be elicited on manipulation of the neck or
palpation of the spinal column. The presence of upper
motoneuron signs in all limbs suggested a lesion between
the 1st cervical (Cl) and 5th cervical (C5) spinal cord
Hematological and serum biochemical analyses were
within normal reference ranges. The dog was anes-
Western College of Veterinary Medicine, University of
Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan
Dr. Hashizume's current address is Westbrook Veterinary
Clinic, 21Fairway Drive, Edmonton, Alberta T6J 2S6.
Cary Hashizume will receive a copy of Saunders Compre-
hensive Veterinary Dictionary courtesy of Harcourt-Brace
Figure 1. Lateral view of cranial cervical vertebrae following
myelogram. Note the accumulation of contrast material at
the dorsal aspect of the subarachnoid space between Cl and C3.
thetized and survey spinal radiographs revealed that
the roof of the vertebral canal at C2 was thinner than nor-
mal and "bowed" dorsally. Cerebrospinal fluid (CSF) was
collected from the cisterna magna; cytologic analysis of
the CSF was normal. A myelogram was performed by
subarachnoid injection of 0.45 mg/kg body weight
(BW) of iohexol (Omnipaque; Sanofi Winthrop
Pharmaceuticals, New York, New York, USA) between
lumbar vertebrae 4 and 5 (L4-L5).
The myelogram revealed an abnormal accumulation
of contrast material dorsal to the spinal cord, from the
caudal margin of the roof of C1 to the roof of C3
Can Vet J Volume 41, March 2000
(Figure 1). The cervical spinal cord was maximally
compressed at C2. The tentative diagnosis was a sub-
A left hemilaminectomy was performed over the
2nd and 3rd cervical vertebrae, and a fluid-filled cyst
was identified in the dorsal aspect of the subarachnoid
space. A midline durotomy released serous fluid. The cyst
was fenestrated by removal of a rectangular section of the
overlying dura mater, which was placed in 10% buffered
formalin solution and submitted for light microscopic
examination. An autogenous fat graft was applied at
the hemilaminectomy site; the epaxial musculature,
subcutaneous tissue, and skin were closed routinely.
Light microscopic examination of the resected dura
mater revealed mild fibrosis of the dura mater with
multiple infolded foci of concentric collagen fibers.
Hypertrophy of the inner fibroblastic layer of the dura
mater was also evident, with the inner surface lined by
single to multilayered flattened cells. No evidence of
prior trauma or active inflammation of the dura mater
was observed, and the diagnosis of arachnoid cyst was
Recovery from surgery was uneventful. The dog was
able to walk within 24 h and was discharged from
the hospital 48 h following surgery. The owners were
advised to restrict the dog's activity for a 4-week period
and to use a shoulder harness in place of a collar while
walking the dog. Four weeks following surgery, the
owners reported that the dog was less ataxic and that the
spontaneous thoracic limb knuckling had decreased.
Five months postoperatively, neurologic examination at
the WCVM-VTH revealed only subtle thoracic limb
hypermetria. Nails on the thoracic limbs were normal,
with no evidence of dorsal scuffing.
Spinal arachnoid cysts are benign dilatations of the
dorsal aspect of the subarachnoid space that are filled
with cerebrospinal fluid (1). The neurological signs
associated with spinal arachnoid cysts are attributable to
focal spinal cord compression and damage (2). Spinal
arachnoid cysts have been reported with increasing fre-
quency in the veterinary literature (2-11), where the
lesions have also been described as subarachnoid cysts
(11), meningeal cysts (4,8), and leptomeningeal cysts (3).
This terminology is misleading due to the presence of
extramedullary expansion and spinal cord cavitation
rather than cyst formation (12). The terms cavitations,
or diverticula, of the meninges (2,4,13) have been advo-
cated as more accurate descriptors of the nature of the
lesion, but most authors continue to use the term "cyst"
to maintain consistency with previous literature (8,13).
Fifteen cases of spinal arachnoid cysts have been
reported in dogs (2-10). No definitive breed, sex, or age
predilections have been determined (8). Most affected
dogs have been less than 18 mo old (9,10), and large
breed dogs are affected more often than are small breed
dogs (10). All reported canine spinal arachnoid cysts have
been located in the cranial cervical or caudal thoracic
levels of the spinal cord (2-10).
Spinal arachnoid cysts develop as accumulations of
cerebrospinal fluid within an extradural or intradural
diverticulum/cavitation of the arachnoid membranes
(8). A concise categorization of spinal meningeal or
arachnoid cysts in humans has been established by
Nabors et al (13) in which 3 types are identified by
operative and light microscopic examination. Type I cysts
are extradural and are without spinal nerve root fiber
involvement; Type II are extradural cysts with spinal
nerve root fiber involvement; and Type III are intradural
cysts (13). To date, all reported cases of spinal arachnoid
cysts in dogs resemble Type III cysts (8).
The etiology of arachnoid cysts in both human and vet-
erinary medicine remains largely unknown, but traumatic,
inflammatory, developmental, and congenital causes
have been suggested (8,14). Arachnoid cysts in humans
may develop secondary to congenital diverticula of the
meninges; traumatic herniation of the arachnoid mem-
branes through the dura mater; chronic arachnoiditis; or
abnormal arachnoid membrane proliferation, creating a
one-way valve between the subarachnoid space and
the cyst and resulting in aberrant CSF accumulation
within the cystic cavity (8,12-15). It is unlikely that a
single etiology exists (2,5,8). In this case, early age of
onset of clinical signs, absence of evidence of trauma or
inflammation, and the subtle enlargement of the spinal
canal at the lesion site suggest a congenital etiology.
Neurological deficits associated with spinal arachnoid
cysts are attributable to focal compression of the spinal
cord (2,3,5,8). Paresis and proprioceptive deficits are
common features (2,8,10). The clinical signs in this
case were more marked in the thoracic than in the
pelvic limbs, with sensory dysfunction (ataxia, hyper-
metria, and loss of conscious proprioception) more
prominent than motor dysfunction (paresis). Predominant
thoracic limb deficits in dogs with cervical spinal cord
disease have been referred to as central cord syndrome
or cruciate paralysis (10). The normal orientation of
spinal cord tracts dictates that the medially located
spinal cord pathways supply the thoracic limbs, while the
more lateral spinal cord pathways extend to the pelvic
limbs (10). A medially located lesion, such as a cyst of
the dorsal subarachnoid space compressing the spinal
cord ventral to it, will compress the medially located
pathways and result in more severe clinical involvement
of the thoracic limbs (10).
The diagnosis of a spinal arachnoid cyst is dependent
on myelography, computerized tomography, or magnetic
resonance imaging (8,10,12-15). Survey spinal radi-
ographs are usually normal, but hemivertebrae or
enlargement of the spinal canal due to cyst expansion
and pressure atrophy of the surrounding vertebral bone
are occasionally identified (3,5,8). Myelographic features
include accumulation of contrast material in the dorsal
aspect of the subarachnoid space and focal spinal cord
attenuation (2-9,1 1).
The current treatment of choice of spinal arachnoid
cysts is surgical removal of the cyst contents and wall
(3-6,8-1 1). Conservative medical management using
anti-inflammatory drugs and restricted exercise has
been reported (2). Surgical decompression of the spinal
cord, via dorsal laminectomy or hemilaminectomy, and
complete surgical excision of the cyst or cyst fenestra-
tion, with or without durectomy, is the preferred method
of treatment (2-6,8-11). Surgical decompression halts
the progression of neurological dysfunction (2-11),
but if it fails to provide permanent CSF drainage, cyst
recurrence and progressive spinal cord damage may
Can Vet J Volume 41, March 2000
develop (7). To limit the risk of arachnoid cyst recur-
rence, surgical marsupialization of the dura mater to the
laminar periosteum has been advocated to provideper-
manent cyst drainage (7).
Spinal arachnoid cysts are abnormal accumulations of
cerebrospinal fluid at sites of dilatation within the dor-
sal subarachnoid space that cause progressive neuro-
logical dysfunction. Conservative medical manage-
ment may result in some clinical improvement, but
decompressive surgery and drainage of the cyst is
I thank Dr. Susan M. Taylor for her interest and guidance.
1. Thomas WB. Disorders of the spinal cord. In: Morgan RV. ed.
Handbook of Small Animal Practice. 3rd ed. Philadelphia:
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2. Dyce J. Herrtage ME. Houlton JEF. Palmer AC. Canine spinal
3. Gage ED. Hoerlein BF. Bartels JE. Spinal cord compression
resulting from a leptomeningeal cyst in the dog. J Am Vet Med
4. Parker AJ. Smith CW. Meningeal cyst in a dog. J AIIm Anim
Hosp Assoc 1974:10:595-597.
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5. Parker AJ Adaims WM. Zachary JF. Spinal arachnoid cysts in the
dog. J Am Anim Hosp Assoc 1983:19:1001-1008.
6. Bentley JF. Simpson ST. Hathcock JT. Spinal arachnoid cxst in a
dog. J Am Anim Hosp Assoc 1991:27:549-55 1.
7. McKee WM. Renwick PW. Marsupialisation of an arachnoid
cystin a dog. J Small Anim Pract 1994:35:108-111.
8. Hardie RJ. Linn KA. Rendano VT. Spinal meningeal cyst in a dog:
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diaeJnosis: Arachnoid cyst in a doe. Vet Radiol Ultrasound
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J Am Anim Hosp Assoc 1997:33:123-125.
12. Gimeno A. Congenital malformations of the spine and spinal
cord. In: Vinken PF. Bruyn GW. eds. Handbook of Clinical
Neurologyzv. Vol 32. Amsterdam: Else ier/North-Holland
Biomedical Pr. 1978:393-448.
13. Nabors MW. Pait TG. Bvrd EB. et al. Updated assessment and
current classification of spinal meningeal cysts. J Neurosurg
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mechanismii. Minim Invasive Neurosur- 1995:38:133-137.
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* Kassal T. Veterinary Helminthology. Butterworth-
Heinemann Inc.. Oxford.
* Poole T. English P. eds. The UFAW Handbook on
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and Advanced Invertebrates. Blackwell Science, United
Kingdom. 1999. 190pp.ISBN 0-632-05132-9.
1999. 265 pp. ISBN
* Gonder JC. Prentice ED. Russow L-M. Genetic
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* NaylorJM. HearingHorse Hearts - An Illustrated
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Saskatoon. 1999. $49.99 CDN + $5.00 shipping.
* Hawk CT. Leary SL. Formulary for Laboratory
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* Rudas P. Veterinary Physiology:A Multimedia
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* Dalton JP. ed. Fasciolosis. Oxford UniversityPress.
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Can Vet J Volume 41, March 2000