One of our readers was give the opportunity to Interview Dr. Marino a Neurologist who is one of the foremost researchers here in the US working to help those who suffer from CM / SM in both dogs and humans. Since this is a rather lengthy interview we will be breaking it up into several parts.
Can you let people know some things that are clinical signs of CM and SM?
Since most patients with syringomyelia have CLM as the underlying causative disorder, it can be difficult to discern which clinical signs are due to the CLM and which are due to the syrinx. Hyperesthesia or pain along the spine is a hallmark clinical sign of syringomyelia. Scratching activity and scoliosis (spine curvature) are also common manifestations. Some dogs will develop clinical signs of spinal cord dysfunction (myelopathy), usually in the cervical (neck) spinal cord region. This can be manifested by difficulty walking in all four limbs. In some cases, dogs with cervical myelopathy due to syringomyelia will develop a condition called central cord syndrome. In this scenario, the front limbs are severely compromised, but the rear limbs are functioning normally or nearly so. Other clinical signs are summarized below.
Clinical signs associated with CLM-SM in dogs.
85.5%
Cervical / cranial hyperesthesia
61.9%
Scratching
47.6%
Diminished menace response
14.3%
Generalized seizures
14.3%
Facial paresis
Does climate make a difference in keeping a dog suffering with the disease more comfortable?
Although it has not been studied in dogs, human patients report a worsening of clinical signs during cold weather, stormy weather and during flight in some.
I have heard that many times a dog can be diagnosed with SM when the MRI was performed for another condition. With the large numbers out there about Cavaliers having CM and SM, what should one do if they discover their dog has this condition?
It is essential they seek counsel from specialists familiar with these conditions. It is common to provide second option consultations on MRI’s at our hospital on behalf of general practitioners and specialists. Unfortunately a lot of misinformation has lead to patients not receiving definitive care because they were simply told to “keep an eye on things”. Syringomyelia doesn’t “ just happen”, it is the result of abnormal CSF fluid flow. The underlying condition must be identified since it is progressive.
If the dog does not have any symptoms should an owner be worried if they learn their Cavalier has this condition?
If a dog has a cerebellar compression without the formation of syringomyelia and subsequent clinical signs, we do not consider the “abnormality” or the “variation of normal anatomy” to be pathologic and therefore do not recommend surgery. However, if there is a compression significant enough to altar CSF flow and result in syrinx formation, we absolutely recommend surgical intervention to restore the normal physiologic flow pattern of the CSF. Very few patients with syringomyelia do not exhibit clinical signs. Results of a recent study indicate that although greater than 50% of dogs examined were reported to be “free of any clinical signs” by their owners, 97% were found to have clinical signs on examination. What this tells us is there needs to be greater education as to what to look for in dogs with Chiari like malformation and syringomyelia. Remember, in people some of the signs like migraines or neck sensitivity are difficult for owners to recognize.
While surgery might not be the answer for every dog do you feel that it helps more dogs then if they were just treated with medications? Does it allow them to live longer lives on average and how much longer? I know that you have pioneer FMD and research using titanium mesh. Ella actually did not have this so scar tissue developed. Can you tell more about this research?
Foramen magnum decompression (FMD) is the preferred treatment for Chiari type I malformation in people. Surgery without cranioplasty is often successful, but 8-30% of patients require reoperation, due to excessive scar tissue formation at the FMD site. When performing FMD, both portions of the occipital bone and the lamina of the C1 vertebral body are removed to provide “boney” decompression. The dura mater that covers the area is frequently abnormal and is either incised (durotomy) or removed. Failure to remove the diseased dura can result in persistent compression, given it acts as a fibrous band constricting the cerebellum. Similar to humans, about 25% of canine patients require re-operation due to excessive post-operative scar tissue formation with FMD alone. It has been reported that worsening clinical signs associated with scar tissue impingement typically occur within 3 months of surgery. Cranioplasty offers a protective covering for the recently decompressed cerebellum and has reportedly decreased the frequency of scar tissue formation in patients after surgery to approximately 1-2%. Currently, 73 of 103 dogs with MRI confirmed CLM treated with FMD with cranioplasty had at least a 1 year follow up and were evaluated. Results of our current ongoing study revealed 62/73 dogs (85%) improved after FMD and cranioplasty and needed no long term medications, with 11/73 (15%) requiring intermittent medication to maintain quality of life. Additionally, although it has been reported the majority of syrinx formations remained unchanged on visual estimation, our objective syrinx evaluation using MRI syrinx volume calculations revealed length measurements preoperatively and 6 months post-operatively in 13 of 21 dogs (62%) had decreased in both average syrinx length and volume, 29.4% and 45.6% respectively, while 4/21 (19%) remained unchanged (Fig 23). Future studies are underway to identify reasons why most dogs experience syrinx resolution while others do not, and if there abnormalities in the latter going unaddressed.