A panicked owner rushes a dog in stating that Fifi just had a seizure. Was that really what occurred? Brain Cardiovascular Temporary brain dysfunction due to abnormal, excessive, hyper-synchronous electrical activity of CNS neurons. A transient loss of consciousness and muscle tone caused by inadequate cerebral oxygenation or perfusion to the reticular activating system of the brainstem Less severe degrees of syncope can also occur resulting in episodic weakness, rear limb weakness, ataxis or collapse without loss of consciousness presyncope or near-syncope Metabolic abnormalities Anemia/hemorrhage Excess cathecholamine stimulation (pheochromocytoma) Addison s disease Hypoglycemia Hypokalemia Hepatoencephalopathy Structural Cardiac Disease Outflow tract obstruction Pericardial effusion/cardiac tamponade Right to left shunt (hypoxia) High intracardiac pressure (impending or early CHF) Arrhythmias Bradyarrhtyhmia Tachyarrhythmia Hypoxia Airway obstruction Laryngeal paralysis Pulmonary hypertension Hypotension Inadequate cardiac output Inadequate vascular tone Blood loss Diuresis/Fluid loss Reflex-Mediated Situational syncoppe Neurocardiogenic syncope Vasovagal syncope As veterinarians, it is our job to try and differentiate what actually occurred compared to the owners perception Tools at our disposal History Physical Exam Preliminary diagnostics Advanced diagnostics 1
One of the most effective tools at differentiating between the events What is happening before, during and after the event? Usually absence of immediate precipitating factor. During rest, mornings. Not associated with exertion, changing position, hot, pain, cough... Pre-event symptoms: Prodrome: May occur hours prior to seizure: display of altered behavior: hiding, nervous. Aura- patient s subjective experience at the onset of seizure. Depends on the area of brain involved: odor- olfactory lobe, fearlimbic cortex, tingling sensation- sensory cortex (ho). Situational syncope Excitement/exercise/stress Cough Gag Deglutition Emesis Micturition Defecation Pain Normal Event can not be interrupted. Type of seizures: Simple partial seizure: focal motor or somatosensory symptoms with maintained consciousness. Complex partial seizure: focal symptoms with altered consciousness (syncope: should not be any focal events). Focal seizures with generalization: focal seizure activity crosses the corpus callosum and affects both hemisphere. Primary generalized seizures. Seizure manifestations: may look like anything. Absence Tonic-clonic Tonic Clonic Atonic Myoclonic Psychomotor Duration of tonic-clonic movements: 30-60 seconds (never >15 sec in syncope). Transition to unconsciousness is immediate (vs. gradual over seconds in syncope). Facial appearance during event: salivation, cyanosis, teeth chattering, fast twitches, biting the tongue. Incontinence: both seizure and syncope. 2
3/20/15 Flaccid collapse Opisthotonus Vocalizing Extensor rigidity Mild myoclonus activity - paddling of limbs as if trying to right themselves Urinating/defecating possible Typically only lasts seconds but can be longer in dogs with arrhythmias May be mildly subdued and slow to recover especially if prolonged cerebral hypoxia Possible increase in respiratory rate or effort depending on cause Otherwise normal with normal mentation Breed Development Delayed return to normal mental status, post ictus. Seconds, minutes to hours: disorientation, confusion, hunger, thirst, blindness, urination, defecation. A complete physical exam and neurologic exam should be performed on an animal presenting for a possible seizure or syncopal event Mental status: Status epilepticus- medical emergency Bright, alert responsive Post ictal Quiet but responsive Obtunded Stuporous Semi comatose Comatose 3
Posture, gait, ambulation Recumbent, decerebrate and decerbellate rigidity Ophistotonus, pleurothotonus Generalized ataxia vs generalized weakness Spinal ataxia Vestibular ataxia Cerebellar ataxia Cranial nerves: facial asymmetry. Proprioception: Paresis (mono, hemi-, para-, tetra-). Spinal reflexes: UMN/LMN Sensorium: hyperesthesia, allodynia. Headache. Focal or asymmetrical abnormality is consistent with neurological disorder Normal neurologic exam Exception: Many animals are older so may have some mild abnormalities from previous problems E.g. T3-L3 mylopathy Can have a normal physical exam Other possible exam findings: Heart murmur Arrhythmia Pale or cyanotic mucous membranes Increased breathing rate or effort Pulmonary crackles or wheezes Poor pulse strength or pulse deficits Baseline bloodwork indicated for both causes CBC, Chemistry (incl electrolytes) Urinalysis Blood pressure Rule out hypo or hypertension as a cause of syncope Cushing s reflex Thoracic Radiographs Evaluate for metastasis Assess cardiac size Rule out congestive heart failure Complete thyroid profile Bile acid assay Urine cortisol/creatinine ratio, LDDST Organic aciduria test Titers and PCRs for neuro- inflammatory diseases Oxytocin NT-proBNP These are typically the more costly tests that require seeing a specialist Every attempt at differentiating between seizure vs. syncope is typically made before electing to proceed with advanced diagnostics Syncope Echocardiogram ECG Holter or Event monitor Seizure EEG MRI CSF evaluation 4
3/20/15 EEG MRI CSF evaluation Echocardiogram ECG Holter Event monitor Brief periods of decreased perfusion of a region of the brain leading to focal, paroxysmal dysfunction. Cause: emboli in blood vessels, stenosis, in ho: precedes a massive stroke. Always maintained consciousness. Lasts 5-50 minutes. Rarely >1 hour. Commonly evidence of vestibular/cerebellar dysfunction: rolling, nystagmus. Vomiting precedes commonly. Ddx idiopathic geriatric vestribular syndrome. Visual loss- difficult to assess around the event in animals. Variety of visual effetcts. Search for cause of CVA (BP, kidney disease, cardiac disease, hypercoagulability syndromescushing s disease, hypothyroidism...). Reoccurring attacks of sleep. Hypothalamus. Sleep/weakfullness regulatory problem, Due to absence or decreased cc of hypocretin hormone Absence or decrease in functional hypocretin receptors. Hypocretin is secreted by emotional stimuli and feeding. With or without catalepsy. Food elicited catalepsy test. Tx: Tricyclic antidepressants increasing adrenerg tone. Imipramine (0.5-1 mg/kg/day ID, desipramine 3 mg/kg BID). Petting the patient during meals. Can be interrupted. Lip smacking, tail chasing, fly biting, licking. 5
Hypoxic brain injury from a cardiovascular cause can induce true seizures 1. Episodes triggered by coughing, activity, excitement, etc. are typically syncope 2. Seizures typically have a pre-ictal and postictal phase but syncope does not. 3. Both seizures and syncope can result in elimination 4. An abnormal neurologic exam makes seizure likely 5. Metabolic causes of collapse must be ruled out 6. Opisthotonus and mild myoclonus activity can occur with syncope but typically not generalized clonic activity 7. Hypersalivation is more typical of seizure 8. Neither syncope or seizure can be interrupted 6