It is said that the only way to correctly diagnose CM and SM is with an MRI. At LIVS it is mentioned that less invasive techniques have been studied to diagnose. Can you tell me about these and especially Thermographic Imaging? I know you wrote a publication on this so is there any hope that this could be used to help breeders/owners catch CM/SM early and promise to help keep the disease under control?
The diagnosis of CLM in dogs and Chiari type I in humans can only be confirmed by MRI which is essential for determining the cause of syringomyelia. Descent of the cerebellum or medulla through the foramen magnum, regional CSF attenuation, cerebellar compression are best evaluated on a T2- weighted sagittal craniocervical MRI. Objective data is not available regarding normal/abnormal standards when interpreting MR images in veterinary patients and differences between breeds may exist. Because considerable variation exists in the interpretation of images between specialists reviewing MR images, caution is advised when reading interpretive reports. Based on the consensus on interpretation by members of the Chiari-Like Malformation and Syringomyelia Working Group, diagnostic standards are likely to be formulated in the near future. Laboratory tests such as hematology, serum chemistry, CSF analysis and urinalysis remain useful in eliminating other possible diagnoses. Advances in MRI technology (CINE-MR) have made possible the analysis of CSF flow which could further our understanding of the effects of CSF flow patterns on syrinx formation. Additionally larger magnets have shortened scan times while enhancing resolution. Limited access to this technology and costs exceeding 2.5 million dollars, has slowed the advancement of knowledge in this area for veterinary patients. Because of the realization that syringomyelia can exist in any region of the spine, it is highly recommended a “whole body MRI” be done to completely assess patients.
Multi slice Helical CT / 3D Reconstruction
Although encroachment on the cerebellomedullary region by portions of the occipital bone has been the focus of many studies, evaluation of the entire skull shape and size utilizing Spiral CT technology with 3D reconstruction is currently underway to identify additional mechanisms of syrinx formation. Some reports describe a volume mismatch between the caudal fossa volume and its neural contents resulting in compression and herniation as the most common finding. Patients with “normal” skull volumes are thought to have a loss of integrity of the brain’s suspensory apparatus allowing for cerebellar slouching into the foramen magnum. Although an association with absent or abnormal frontal sinus formation has been reported, it has not been determined to be a causal relationship. This advanced imaging technique will be able to identify volume or conformational abnormalities in affected patients. Regardless of the cause, the focus is now on correcting the flow of CSF as the malformation affects its normal passage around the brain and spinal cord and leads to the syrinx formation.
Thermography is a non-invasive imaging technique involving the recording of cutaneous thermal patterns. This imaging modality provides information about the function of the sympathetic nervous system. Because of recent advances in technology and the ability to image patients without the need for sedation, thermogaphy has potential use as a screening test for CLM in dogs. Loughin et al recently concluded a study documenting the reproducibility of image generation in normal canine limbs in 2007. A current study by the same authors is attempting to establish a thermographic imaging protocol for dogs suspected of having CLM, to identify thermal imaging patterns for various regions of interest (ROI), to evaluate changes in thermal pattern and compare the results to those of brain auditory evoked response tests (BAER) and MRI findings, considered the standard for CLM in dogs. The complete analysis of thermal patterns is on going; however, preliminary results revealed lower temperature thermographic patterns in dogs with abnormal MRI findings compared with the dog with a normal MRI. Magnetic resonance imaging findings classified as mild, moderate and severe correlated with thermographic findings, 100%, 50%, and 0% of the time respectively. Based on these very preliminary findings, thermography may be a viable imaging modality to use as a screening tool to detect CLM in dogs.
Brain Auditory Evoked Response (BAER)
Thirty-eight Cavalier King Charles Spaniels were evaluated with BAER as part of the aforementioned ongoing study. One dog had a normal MRI, BAER, and thermographic evaluation. Twenty-three dogs without clinical signs had abnormal MRI findings with 16 of the 23 dogs (69.6%) also having abnormalities with BAER testing. Fourteen dogs with clinical signs had abnormal MRI findings and 13 of the 14 dogs (92.8%) also had abnormal BAER tests. BAER testing may play a more useful role in screening “clinical” dogs rather than dogs without clinical signs.
I have found that research often leads to more questions. What are some things that are being studied to help in diagnosing and medically managing dogs with CLM and also SM?
Craniocervical junction abnormalities (CJAs) in small breed dogs are being increasingly recognized as common and challenging disorders. The term CJA serves as an “umbrella” term for a variety of malformations that occur in the craniocervical region of small dogs including Chairi-like malformation. It is often difficult to impossible to discern what specific structure or structures cause the cerebellar compression on MR imaging, as bone is poorly visualized on MR images. In a CJA disorder of humans known as basilar invagination (BI), a rostrally displaced C1 dorsal arch can cause cerebellar compression. A similar condition has been recently described in dogs and is referred to as atlanto-occipital overlapping (AOO). Computed tomography is often performed along with MR imaging in human cases of CJA in order to ascertain what specific structures are causing compression. Similarly, at the Canine Chiari Institute, we have been routinely performing CT immediately following the MR imaging of canine patients with CJA. In our clinical experience, cerebellar compression (CC), defined as an indentation of the cerebellum, medullary kinking (MK) defined as an elevation of the medulla at the cervicomedullary junction by the dens, and dorsal compression of the C1/C2 spinal cord (DC) are common findings on MR screening images of dogs for suspected CLM. The conclusion of a recent study indicated that non CKCS dogs with CLM and a DC or a MK should be assessed for the presence of AOO; CKCS dogs with a CC compression index over 16.1% or non CKCS dogs over 12.3% should be assessed for the presence of AOO. Failure to recognize and address AOO in dogs having surgery for CLM, may result in poor outcomes.
Other studies include:
Thermographic Imaging in Dogs with Intervertebral Disc Disease
Grossbard BP, Loughin CA, Marino DJ
Thermographic imaging is a non-invasive method used to screen animals for multiple medical problems. This study documents the use of thermal imaging to screen small breed dogs for possible herniated disc disease. Dogs with confirmed herniation based on MRI results are compared to dogs that have no evidence of a herniated disc. We also look at the usefulness of thermography to predict the site of herniation.
Treatment of Dogs with Primary Secretory Otitis Media
Grossbard BP, Loughin CA, Marino DJ
Primary secretory otitis media, also known as PSOM, is a disease of the inner ear. A mucous plug collects behind the ear drum, and can cause pain and scratching. Reported treatments have had variable success, and the mucous plug tends to recur. This study explores initial treatment with myringotomy followed by clavamox for 2 weeks.
Comparison between CT and MR for the Diagnosis of Primary Secretory Otitis Media in Dogs
Govier S, Loughin CA, Marino DJ
Primary secretory otitis media, also known as PSOM, is a disease of the inner ear. A mucous plug collects behind the ear drum, and can cause pain and scratching. Diagnosis has primarily depended on visualization of a pink swollen ear drum on examination of the ear canal. This type of examination can lead to missed diagnosis of PSOM since it is difficult to visualize this change. Recent studies have found that PSOM can easily be seen on a MRI, but MRIs are expensive and not widely available. This study looks at the accuracy of CT to diagnose PSOM.
The Prevalence of Primary Secretory Otitis Media in a Population of Cavalier King Charles Spaniels diagnosed with chiari-like malformation
Lugones M, Loughin CA, Marino DJ
Cavalier King Charles Spaniels constitute a breed that has a predisposition for PSOM and CLM, but “can these dogs have both diseases at the same time?” This study looks at a population of dogs being evaluated for CLM, and determines how prevalent PSOM is in this group of dogs.
Morphometric Features of the Craniocervical Junction Region in Dogs with Suspected Chiari-like Malformation Based on Combined MR and CT Imaging: 274 Cases (2007-2010)
Marino DJ, Loughin CA, Dewey CW, Marino LJ, Sackman J, Lesser M, Ackerman M
Evaluation of MRIs for CLM have mainly been based on the doctor’s opinion on how compressed and herniated the cerebellum may be. This kind of evaluation leads to considerable variability, resulting in disagreement among doctors. In order to make MRI evaluations more consistent, measurements made in the region of the skull and vertebrae of the neck have been developed. This paper reports the consistency of these new measurements.
The Effect of Foramen Magnum Decompression and Cranioplasty on Syrinx Volume in Dogs with Chiari-like Malformation
Loughin CA, Marino DJ, Dewey CW
Syringomyelia, also called SM or syrinx, has been documented as a secondary occurrence to CLM. Based on multiple theories and the results of research in humans, we suspect that the syrinx will slowly regress after decompressive surgery. This paper looks at a group of dogs diagnosed with CLM and SM, and follows them for one year after surgery to see what happens to the length and volume of the syrinx over time.
Syrinx Location in Dogs with Chiari-like Malformation having Brain and Whole Spine MRI
Dewey CW, Loughin CA, Marino DJ
MRI studies of dogs thought to have CLM have included mainly the skull and neck, but does the syrinx exists further down the spinal cord? This study looks at a group of dogs with CLM and SM to see how far the syrinx can extend.
Histologic Findings on Dural Biopsies in Dogs with Foramen Magnum Decompression and Cranioplasty for Chiari-like Malformation
Loughin CA, Marino DJ, Peters R
Dural biopsies performed in humans with chiari-like malformation have shown thickening of the dura mater. Some of this thickening has even been described as “bone-like”. Do dogs with CLM exhibit the same changes of the dura mater at the site of compression? This paper evaluates the biopsy reports of a group of dogs that have undergone surgery for CLM to determine if the dura develops “bone-like” qualities.