The purpose of this study was to describe clinical results of a FMD procedure in 16 dogs with COMS.Cases were restricted to dogs with MRI evidence of COMS and no other neurologic disorders.
Quote: "Hydromyelia is a dilation of the spinal cord central canal. This surgical technique was performed on 4 Cavalier King Charles spaniels diagnosed with Chiari type I malformation by symptoms (scratching of neck region) and by MRI. The fourth dog was euthanized within 24 hours after surgery at owners request due to progressive seizures and decreased capability of oxygen saturation. Therefore, in human medicine, a suboccipital craniectomy and cranial dorsal laminectomy with opening of the dura mater is the procedure of choice for surgical treatment of CIM.Five of 6 dogs with scratching behavior prior to FMD continued to do so postoperatively; two of these five dogs required medical therapy to control scratching. On the basis of the planned post hoc t-tests of postrandomization means, there was a significant difference between treatment groups on day 42 (P 5.030), with the amantadine group being more active. This study did not identify a smaller caudal fossa in an asymptomatic cavalier King Charles spaniel population with syringomyelia.Mean duration of signs prior to FMD was 3.8 wks for the resolved group, and 78.08 wks for the improved group. Conclusions and Clinical Importance: In dogs with osteoarthritic pain refractory to an NSAID, physical activity is improved by the addition of amantadine. Stalin, Clare Rusbridge, Nicolas Granger, and Nick D. Ultrasonography probably has a low sensitivity for diagnosis of Chiari-like malformation/syringomyelia." .Other specific abnormalities included cervical hyperesthesia (13), diminished menace responses (7), positional strabismus (7), excessive scratching behavior (6), torticollis (3), abnormal mentation (2), “fly-biting” episodes (2), head tilt (2), chewing at the paws (2), excessive licking (1), eye rubbing (1), and generalized seizures (1).
Mean duration of clinical signs prior to surgery was 32.19 wks (1-208 wks). One dog had worsening of a head tilt, which resolved in three weeks. Quote: "Results: Of the 16 [CKCS] dogs in the study, 7 had syringomyelia (43.7%).
The relationship between occipital dysplasia and syringo/hydromyelia in these dogs remains unclear, however, similar associated abnormalities are occasionally found in humans with Chiari malformation." . Response to diuretic therapy was moderate but surgical decompression may offer better long term prognosis." . The dogs with these abnormalities had a wide variety of neurological signs, but there was no apparent correlation between the neurological signs and the severity of cerebellar herniation, syringohydromyelia or hydrocephalus." . Study Design— Four CKCS diagnosed by Magnetic resonance imaging (MRI) of SHM because of cerebellar tonsil herniation and not responsive to medical therapy underwent a suboccipital craniectomy and dorsal laminectomy of C1 (2 dogs) and of C1 and partial C2 (2 dogs) with durotomy and placement of a dural graft. Both direct bony compression and progressive meningeal hypertrophy at the level of the posterior (dorsal) cervicomedullary junction are believed to lead to abnormalities of cerebrospinal fluid flow dynamics.
While occipital dysplasia alone is not thought to cause any clinical abnormalities, the dogs of this report suggest that intramedullary central nervous system abnormalities may be present concurrently with occipital dysplasia and should be considered as a possible cause of the clinical signs. Mechanical obstruction at the craniocervical junction, altering CSF flow dynamics, may lead to syrinx formation. Abnormalities compatible with such a malformation were identified by magnetic resonance imaging in 39 cavalier King Charles spaniels with neurological signs and in one neurologically normal cavalier King Charles spaniel that was examined postmortem. Vermeersch K, Van Ham L, Caemaert J, Tshamala M, Taeymans O, Bhatti S, Polis I. This technique is used with great success in human medicine. Quote: "Chiari type 1 malformation in humans is a congenital abnormality of the caudal occipital bone, resulting in overcrowding of the caudal fossa and compression at the level of the cervicomedullary junction.
Aspects of the human disorder and information from previously published canine cases are discussed.
However, the focus is on the 30 recently reviewed cases. Quote: "Caudal occipital malformation syndrome (COMS) is the canine analog of human Chiari I malformation.
Syringohydromyelia was evident on MRI in 15/16 dogs (93.75%). Another dog experienced neck pain after the initial FMD (resolved in four wks), and was nonambulatory tetraparetic following repeat FMD. Quote: "Ultrasonographic evaluation of the spine, especially of the spinal cord, has been rarely reported in dogs. All dogs had cerebellar herniation, suggesting Chiari-like malformation and also a tendency to occipital dysplasia.