Cerebellar Infarcts -- Strokes --
in the Cavalier King Charles Spaniel
Cavalier King Charles spaniels appear predisposed to develop cerebellar infarcts, or strokes. Dr. Curtis Dewey has attributed them to the “frequent presence of caudal occipital malformation syndrome (COMS) in these dogs.”
In a 2005 study of several breeds of dogs with brain infarcts, the researchers found that CKCSs were "overrepresented" (18% of the entire group of dogs studied) and opined that the reason may be mitral valve disease (MVD) or blood platelets or Chiari-like malformation. They stated:
"The reasons for overrepresentation of CKCS are unclear but may be due to the prevalence of heart disease, alterations in coagulation and platelet morphology, connective tissue pathology, or anatomic variation (ie, Chiari malformation) recognized in this breed. CKCS have a high prevalence of mitral valve regurgitation, as well as platelet abnormalities, 40 which might predispose them to cardioembolic infarction. Cavalier King Charles Spaniels also have a high prevalence of Chiari type malformation, which may alter vertebral-basilar blood flow and predispose them to strokes. This malformation was identified in 3 of the 6 CKCS of this study. A pathophysiologic link among the above conditions frequently seen in CKCS and the occurrence of ischemic stroke is speculative and remains to be further studied."
Dr. Dewey has responded to that hypothesis by stating:
"It has been postulated that this predisposition may be related to this breed's propensity to develop heart disease, inherited platelet abnormalities, or to local aberrations in regional arterial (e.b., basilar artery) blood flow due to caudal occipital malformation (COMS), which is common in the breed. ... In the author's experience, the combination of COMS and cerebellar infarct is common in the CKCS, whereas combinations involving cardiac disease and platelet abnormalities are not.”
A cerebellar infarct is a localized area of typically wedge-shaped dead tissue (see MRI image at right), called a lesion, within the cerebellum of the brain, which results from the sudden rupture of one of the cerebellar arteries, causing interference with normal blood flow through the area. Such cessation of blood flow may also be referred to as a cerebellar stroke. The effect of a stroke, and the creation of the infarct, are caused by the lack of normal oxygen delivery from the blood flow.
The onset of symptoms of a cerebellar infarct usually is quite sudden and dramatic. The cavalier may be behaving normally one minute, and then in an instant, become unsteady, un-coordinated, nauseous, walk uncontrollably in small circles, or even faint and fall over. The dog may tilt its head, have facial paralysis, lose its vision or control of its bowels, or change its temperament.
Some symptoms may progress over the first twelve hours, presumably due to brain swelling, while others may disappear quickly. Most symptoms should begin to lessen within a day or two.
Cerebellar infarcts should be suspected in any case in which the onset of symptoms is sudden and otherwise unexplained. The dog should be taken to a veterinary clinic immediately; examination by a neurologist would be preferable. The veterinarian should conduct a complete neurological examination, in addition to blood pressure measurement, normal blood work and urinalysis, x-rays, and possibly an ultrasound and endocrine and thyroid profiles.
The symptoms may be confused with those of paradoxical vestibular syndrome, particularly the head tilt, which is the most consistent sign of unilateral vestibular dysfunction, and ataxia – loss of muscle coordination – and nystagmus, which is an involuntary rhythmic oscillation of the eyeball.
The only accurate way to diagnose an infarction is using magnetic resonance imagine (MRI), and to a limited extent, computed tomography (CT), to obtain scans of brain images. Early enough CT imaging should enable the veterinarian to determine whether the infarct was caused by a burst blood vessel (hemorrhagic), but MRI is the best device for identifying a shut down blood vessel (ischemic), which will better determine the treatment protocol.
(The image at right is an MRI scan of a CKCS skull, showing a wedge-shaped cerebellar infarct at lower right of the brain. Image from The Downs Veterinary Practice.)
“There appears to be a predisposition for spaniel breeds, especially cavalier King Charles spaniels, to develop cerebellar strokes. This is suspected to be due to frequent presence of caudal occipital malformation syndrome (COMS) in these dogs, with associated interference with normal basilar artery flow.”
If the veterinarian is able to determine the underlying cause of the infarction, it should be treated promptly. Initially, mannitol may be administered intravenously to overcome any brain swelling. Mannitol is the alcohol form of the sugar, mannose, and it is an osmotic diuretic and a mild renal vasodilator. It is used to treat excessive intra-cranial pressure and to expand blood vessel openings in the brain.
If systemic hypertension is found, enalapril maleate (Enacard, Vasotec), or another ACE-inhibitor may be prescribed. ACE-inhibitors block the angiotensin converting enzyme, which is necessary to produce a substance that causes blood vessels to tighten. So, ACE-inhibitors serve to relax the blood vessels, thereby lowering the blood pressure and increasing the supply of blood and oxygen to the brain.
Amlodipine (Norvasc) may also be administered. Amlodipine is a calcium channel blocker which relaxes blood vessels so that the blood can flow more easily.
Nicergoline (Fitergol, Sermion) is an alpha-blocking cerebral vasodilator which is a vasodilator that improves blood flow to the brain and stimulates the use of oxygen and glucose. It also blocks serotonin and dopamine receptors. It is used to treat migraine headaches that are of vascular origin and other problems of a vascular nature, such as dizziness and auditory problems.
The prognosis is guarded if the symptoms are very severe and prolonged. However, dogs with less severe signs have shown rapid and dramatic recoveries.
MRI appearance of cerebrovascular disease in seven spaniels. Mcconnell, J. F., Garosi, L., Dennis, R., Platt, S. R. & Abramson C. J. 2003 BSAVA Congress; pg 568.
Cerebellar Infarcts in Two Dogs Diagnosed With Magnetic Resonance Imaging. Jason M. Berg and Richard J. Joseph. J Am Anim Hosp Assoc.2003;39:203-207. Quote: "Two dogs presented with severe, peracute-onset, neurological signs. Neuroanatomical localization was cerebellovestibular. Magnetic resonance imaging (MRI) was performed and revealed focal, wedge-shaped lesions in the cerebellum. Diagnosis of cerebellar infarctions was made based on peracute-onset, clinical signs, MRI, and outcome as well as ancillary diagnostic information. Both dogs recovered completely. Cerebellar infarction should be included in the differential of any dog with peracute-onset, central cerebellovestibular signs regardless of severity of clinical signs. Outcome was excellent in these dogs."
Magnetic Resonance Imaging Findings of Presumed Cerebellar Cerebrovascular Accident in Twelve Dogs. J. F. McConnell, L. Garosi, S. R. Platt. Vety. Radiology & Ultrasound. Jan. 2005; 46(1):1-10. Quote: "The magnetic resonance imaging (MRI) findings of presumed cerebrovascular accident in 12 dogs are described ... four Cavalier King Charles Spaniels ... . Fourteen lesions were seen, commonly (11 of 14) within the gray matter of the cerebellar hemispheres or vermis. Thirteen lesions were hyperintense on T2-weighted images (in 11 dogs) and one was hypointense. Eleven of 14 lesions were within the region supplied by the rostral cerebellar artery or one of its main branches and there was no, or minimal, mass effect. Contrast enhancement was only seen in six lesions and was mild in all. Gradient-echo images provided additional information in two dogs. The appearance of infarction in dogs with diffusion-weighted images (DWI) is similar to that in humans, and provided supportive evidence for the diagnosis of infarction in five dogs. The use of gradient-echo and DWI is recommended for the evaluation of suspected cerebrovascular accidents in dogs. Six of the 12 affected animals were spaniels or spaniel crosses, suggesting a possible breed predisposition."
Results of Diagnostic Investigations and Long-Term Outcome of 33 Dogs with Brain Infarction (2000–2004). L. Garosi, J.F. McConnell, S.R. Platt, G. Barone, J.C. Baron, A. de Lahunta, and S.J. Schatzberg. J.Vet.Intern.Med. 2005;19:725-731. Quote: "Medical records of 33 dogs [6 cavalier King Charles spaniels] presented for acute onset, nonprogressive, intracranial dysfunction that had a magnetic resonance imaging diagnosis of brain infarction were reviewed. Postmortem confirmation of brain infarction was available in 10 dogs. All dogs were evaluated by CBC, serum biochemistry, thyroid and adrenal testing, urinalysis, thoracic and abdominal imaging, and cerebrospinal fluid analysis. Results of coagulation profile and arterial blood pressure were available in 32/33 and 28/33 dogs, respectively. On the basis of the imaging findings, infarcts were classified depending on their type (territorial or lacunar) and location within the brain (telencephalic, 10/33; thalamic/midbrain, 8/33; cerebellar, 15/33). ... No age, sex, or breed predisposition was identified for brain infarction in dogs in this series. Cavalier King Charles Spaniels (CKCS) and Greyhounds, however, appeared overrepresented (18% and 15%, respectively) compared with CKCS and Greyhounds presented to the neurology service (3.5% and 0.87%, respectively) and the hospital population (3% and 0.66%, respectively) during the same study period. The reasons for overrepresentation of CKCS are unclear but may be due to the prevalence of heart disease, alterations in coagulation and platelet morphology, connective tissue pathology, or anatomic variation (ie, Chiari malformation) recognized in this breed. CKCS have a high prevalence of mitral valve regurgitation, as well as platelet abnormalities, 40 which might predispose them to cardioembolic infarction. Cavalier King Charles Spaniels also have a high prevalence of Chiari type malformation, which may alter vertebral-basilar blood flow and predispose them to strokes. This malformation was identified in 3 of the 6 CKCS of this study. A pathophysiologic link among the above conditions frequently seen in CKCS and the occurrence of ischemic stroke is speculative and remains to be further studied. ... Dogs with concurrent medical conditions had significantly shorter survival times than those with no identifiable medical condition and were significantly more likely to suffer from recurrent neurologic signs because of subsequent infarcts."
Vascular Encephalopathies. C.W. Dewey. 50° Congresso Nazionale Multisala SCIVAC, 2005. Quote: “There appears to be a predisposition for spaniel breeds, especially cavalier King Charles spaniels, to develop cerebellar strokes. This is suspected to be due to frequent presence of caudal occipital malformation syndrome (COMS) in these dogs, with associated interference with normal basilar artery flow.”
Neurological diseases of the Cavalier King Charles spaniel. Rusbridge, C. J Small Animal Practice, June 2005, 46(6): 265-272. "CKCSs seem to have an increased tendency towards cerebrovascular disease (McConnell and others 2003), particularly infarction of the rostral cerebellar artery. Affected dogs present with signs of acuteonset, rapidly progressive central vestibular syndrome. Rostral cerebellar artery infarction in humans is associated with cardiogenic embolism and major artery occlusive disease such as carotid artery dissection (Yin and others 1994). The CKCS is predisposed to mitral valve disease Haggstrom and others 1992), increased platelet aggregation (Olsen and others 2001) and arterial disease (Buchanan and others 1997), all of which offer some explanation for a tendency towards cerebrovascular disease. In the UK, any CKCS presented with signs of intracranial haemorrhage or infarction should be screened for Angiostrongylus vasorum. This parasite can result in bleeding and coagulation disorders, and the CKCS appears to be predisposed to infection (Chapman and others 2004)."
Clinical and Topographic Magnetic Resonance Characteristics of Suspected Brain Infarction in 40 Dogs. L. Garosi, J.F. McConnell, S.R. Platt, G. Barone, J.C. Baron, A. de Lahunta, and S.J. Schatzberg. J Vet Intern Med 2006;20:311–321. Quote: "Medical records of 40 dogs [including 8 cavalier King Charles spaniels] presented for evaluation of acute-onset, nonprogressive, intracranial dysfunction by means of magnetic resonance imaging (MRI) diagnosis of brain infarction were reviewed. Location of the brain infarcts was: 11 of 38, telencephalic; 8 of 38, thalamic/midbrain; 18 of 38, cerebellar; and 3 of 38, multifocal. Telencephalic infarcts developed within the territory of the middle cerebral (4/11), rostral cerebral (2/11), and striate (5/11) arteries. Thalamic/midbrain infarcts developed within the territory of perforating arteries of the caudal portion of the thalamus and rostral portion of the brainstem (8/8). All cerebellar infarcts (18/38) were within the territory of the rostral cerebellar artery or one of its branches. All infarcts appeared nonhemorrhagic, with marked contrast enhancement observed in only 3 of 38 dogs, all of which were imaged more than 7 days after the onset of signs of neurologic dysfunction. Diffusion-weighted imaging (DWI) sequences were available from 6 dogs, all imaged within 5 days of the onset of signs of neurologic dysfunction. Suspected infarcts were hyperintense on DWI sequences and were hypointense on the apparent diffusion coefficient map. Telencephalic infarcts caused abnormal mental status, contralateral postural reaction deficit, contralateral nasal hypalgesia, contralateral menace deficit, and ipsilateral circling. Thalamic/midbrain infarcts caused contralateral or ipsilateral postural reaction deficit, contralateral menace deficit, ipsilateral head tilt or turn, nystagmus, ventrolateral strabismus, and anisocoria. Cerebellar infarcts caused ipsilateral asymmetric cerebellar quality ataxia, head tilt, intermittent opisthotonus, nystagmus, and ipsilateral menace deficit with apparent normal vision."
Suspected cerebellar infarcts in 4 dogs. John C. Irwin, Curtis W. Dewey. J Vet Emer & Crit Care; Sept 2007; 17(3):268-274. Quote: “Objective: Reports of cerebellar infarction in veterinary literature are rare. Documentation and descriptions of cerebellar infarction in human literature have been well described. Brain lesions suspected to be infarcts have been recognized with magnetic resonance imaging (MRI). ... Four dogs presented ... with the history of acute onset cerebellovestibular dysfunction [including a cavalier King Charles spaniel]. All animals were imaged using a 0.5 T super-conducting Magna GE MRI unit. Suspected cerebellar infarction was diagnosed in all dogs based on history, physical examination, and MRI findings. Further diagnostics were performed based on the individual case and owner compliance. Functional recovery was favorable in 3 dogs. One dog was euthanized shortly following the onset of neurological dysfunction. ... Cerebellar infarction appears to have characteristic MRI features. Affected tissue within the cerebellum is typically wedge-shaped with low signal intensity in T1-weighted images, high signal intensity in T2-weighted images, subtle rim enhancement without central contrast enhancement in T1 post-gadolinium, and selectively hyperintense in fluid-attenuated inversion recovery images. Anatomic regions serviced by rostral cerebellar arteries are affected. Vascular risk factors as compared with reports in human literature are also discussed.”
A Practical Guide to Canine and Feline Neurology. Curtis W. Dewey. John Wiley & Sons; 2008; 4-6, 194-195. Quote: ""Breed-associated neurologic abnormalities of dogs and cats. ... Cavalier King Charles Spaniels ... Cerebellar infarct". pp. 4-6. “Cerebellar infarcts appear to be most common in small breed dogs, most notably the Cavalier King Charles Spaniel (CKCS). It has been postulated that this predisposition may be related to this breed's propensity to develop heart disease, inherited platelet abnormalities, or to local aberrations in regional arterial (e.b., basilar artery) blood flow due to caudal occipital malformation (COMS), which is common in the breed. ... In the author's experience, the combination of COMS and cerebellar infarct is common in the CKCS, whereas combinations involving cardiac disease and platelet abnormalities are not.”
Ischaemic and haemorrhagic stroke in the dog. A Wessmann, K Chandler, L Garosi. Vety.J. June 2009; 180(3):290-303. Quote: "Cerebrovascular disease results from any pathological process of the blood vessels supplying the brain. Stroke, characterised by its abrupt onset, is the third leading cause of death in humans. This rare condition in dogs is increasingly being recognised with the advent of advanced diagnostic imaging. ... Cavalier King Charles Spaniels and greyhounds were overrepresented in one study of brain infarcts (Garosi et al., 2005a). Small breed dogs were more likely to have cerebellar territorial infarcts and large breed dogs were more likely to have lacunar thalamic-midbrain infarcts ... Magnetic resonance imaging (MRI) is the first choice diagnostic tool for stroke, particularly using diffusion-weighted images and magnetic resonance angiography for ischaemic stroke and gradient echo sequences for haemorrhagic stroke. An underlying cause is not always identified in either humans or dogs. Underlying conditions that may be associated with canine stroke include hypothyroidism, neoplasia, sepsis, hypertension, parasites, vascular malformation and coagulopathy. Treatment is mainly supportive and recovery often occurs within a few weeks. The prognosis is usually good if no underlying disease is found."
Computed tomography diagnosis of eight dogs with brain infarction. AEH Paul, Z Lenard, CS Mansfield. Australian Vet J. Oct. 2010; 88(10): 374-380. Quote: “Objective: Medical records of eight dogs [two Cavalier King Charles Spaniels (CKCS)] presenting with acute onset of neurological signs and a diagnosis of brain infarction as determined by computed tomography (CT) imaging were reviewed. Results: Ischaemic infarction in the territory of the rostral cerebellar artery was identified in three spaniel-breed dogs. All cerebellar infarcts were non-haemorrhagic. Telencephalic infarcts were identified in five dogs, in the territories of the middle cerebral artery (2/5) and rostral cerebral artery (3/5). One of these dogs had an ischaemic infarction, but all other infarctions appeared haemorrhagic. All dogs were geriatric (≥8 years old), with concurrent medical conditions identified in six dogs. One dog was euthanased after diagnosis because of the severity of its neurological signs and one dog was euthanased as a result of associated renal disease 2 months after diagnosis. Six dogs were alive at least 1 year after diagnosis. Conclusions CT is useful in the diagnosis of cerebrovascular accident in dogs, which can present as a spectrum of images with early changes in attenuation and subtle mass effects detected after infarction. CT is particularly sensitive for detecting haemorrhagic infarction, but under-represent ischaemic and lacunar infarctions when compared with MRI.”
Feline Cerebrovascular Disease: Clinical and Histopathologic Findings in 16 Cats. Ulrike Michal Altay, Geoff C. Skerritt, Monika Hilbe, Felix Ehrensperger, and Frank Steffen. J.Amer.Anim.Hosp.Assn. March 2011;47(2):89-97. Quote: "... Cerebellar infarcts in Cavalier King Charles spaniels have been reported with increasing frequency ... ."
Clinical and topographic magnetic resonance imaging characteristics of suspected thalamic infarcts in 16 dogs. Rita Gonçalves, Inés Carrera, Laurent Garosi, Peter M. Smith, J. Fraser McConnell, and Jacques Penderis Vet J, April 2011, 188(1)39-43. Quote: “Sixteen dogs with acute-onset, non-progressive signs of brain dysfunction and magnetic resonance imaging (MRI) characteristics compatible with thalamic infarction are described. ... There were 3 Cavalier King Charles spaniels (CKCS) ... Topographically the MRI lesions could be grouped in three thalamic regions, namely, paramedian (8/16), extensive dorsal (5/16) and ventrolateral (3/16). Paramedian lesions resulted in signs typical of vestibular dysfunction. Extensive dorsal lesions were associated with vestibular ataxia, circling and contralateral menace response deficits. Ventrolateral lesions resulted in circling and contralateral proprioceptive deficits. In several dogs, regions other than the thalamus were also affected: four extended into the midbrain; six extended to the internal capsule, and two dogs had a second lesion in the cerebellum. Three clinical syndromes were identified in association with thalamic infarction. These signs varied somewhat, most likely because lesions were not confined to specific nuclear boundaries and involved different combinations of thalamic nuclei."
Concurrent Medical Conditions and Long-term Outcome in Dogs with Nontraumatic Intracranial Hemorrhage. Mark Lowrie, Luisa De Risio, Ruth Dennis, Francisco Llabres-D´iaz, Laurent Garosi. Vety Radiology & Ultrasound. Apr 2012; 53(4):381-388.
Spontaneous ischaemic stroke in dogs: clinical topographic similarities to humans. H. Gredal1, G. C. Skerritt, P. Gideon, P. Arlien-Soeborg, M. Berendt. Acta Neurologica Scandinavica. Sept. 2013;128(3):e11–e16. Quote: "Background: Translation of experimental stroke research into the clinical setting is often unsuccessful. Novel approaches are therefore desirable. As humans, pet dogs suffer from spontaneous ischaemic stroke and may hence offer new ways of studying genuine stroke injury mechanisms. Aims: The objective of this study was to compare clinical symptoms and infarct topography of naturally occurring ischaemic stroke in pet dogs with human ischaemic stroke. Methods: Medical records and magnetic resonance imaging (MRI) of 27 dogs with spontaneous ischaemic stroke [including cavalier King Charles spaniels] were retrospectively investigated with respect to clinical symptoms and infarct topography. Symptomatology and MRI characteristics were compared with humans. Results: Seventy per cent were diagnosed with middle cerebral artery (MCA) occlusions. Motor dysfunction or sensory-motor dysfunction was reported in 78%, including specific signs of contra-lateral motor dysfunction in 11 of 27 (40%). Seizures were reported in 15 of 27 cases (56%). Conclusions: Spontaneously occurring ischaemic stroke in dogs share characteristics with human ischaemic stroke in terms of clinical symptoms and infarct topography. Investigating pet dogs with spontaneous ischaemic stroke may provide an alternative approach to the research of stroke injury mechanisms as they occur naturally, and should be further investigated."
Do Dogs Have Strokes? Cerebrovascular Accident. Laurent Garosi. 11th ECC UK 2014 Lecture, Vet. Times. November 2014.