A total of 37 cases (23 females and 14 males) were included in this study. All of the dogs were living indoors with their owners as family members, rather than in outdoor kennels or in separate doghouses. 16 of the dogs were active working dogs, implying that they were trained to compete in obedience, tracking, searching, or were patrol dogs in the Swedish army. Median bodyweight was 42 kg (range 31–60 kg). Ten of the dogs were neutered surgically; two additional dogs were chemically neutered. Most of the dogs were characterised by their owners as active (27), friendly (31) and calm (14) by nature. A few dogs were characterised as nervous (5), shy (1) or aggressive (3). It was possible to choose several options to describe each dog.
The median age at onset of seizures was 36 months (range 8–84 months), seemingly with two peaks: At 18 and 36 months of age (Fig. 1). Twenty-three of 37 dogs (62.2 %) had their initial seizure by 36 months of age. The date of seizure onset was not reported for one dog and that dog was therefore excluded from the study. The follow-up time from the initial seizure until study inclusion varied from 1 to 60 months with a median follow-up time of 10 months. In total, 26/37 (70.3 %) of the included dogs had a follow-up time of >4 months without progression to more serious illness or SE, and these dogs fulfilled the criteria for IE. Seizure frequency ranged from several seizures per week to one per year.
Thirty-three of 35 (94.3 %) of the dogs appeared to lose consciousness during the seizures, and 26/27 (96.3 %) did not respond to contact (when the owner called their name) during the seizures. The clinical presentations of the seizures are summarized in Table 1. The dogs suffered from generalized tonic–clonic seizures with the following signs; Stiffness in neck and legs, unconsciousness, salivation, shaking, gazing, falling to the side, muscle twitching/shivering, chewing, contraction of facial muscles, and urination (whereas defecation was uncommon). The most common behaviours reported in the postictal phase were confusion and disorientation, restlessness and tiredness (Table 2).
Twenty of 37 (54 %) of the dogs had experienced cluster seizures (>1 seizure in 24 h). The mean number of seizure days (24 h), for the time-period included in the questionnaire, was 12.2 seizure days (range 2–67 seizure days). Only 24 owners described how the seizure frequency changed over time, (independently of antiepileptic medication): For 8/24 (33.3 %) of the dogs the frequency had decreased, for 11/24 (45.8 %) the frequency was stable, and for the remaining 5/24 (20.8 %) the frequency had increased. For 19/32 (54.9 %) of the dogs, the duration and intensity of the seizures remained the same, while it had increased for 5/32 (15.6 %), and decreased for 8/32 (25 %). The changes in seizure frequency, and intensity and duration of the seizures were based on the owners’ assessment. The dogs commonly started to seizure while resting (23/36) or sleeping (20/36). Only three of the 36 dogs (8.3 %) experienced seizures during activities such as walking or training. For the females, five of 23 bitches tended to have seizures around the time of heat; two during heat, and three within 2 months after heat. One male dog was reported to have more frequent seizures when there were females in heat in the neighbourhood.
Thirty of 37 (81.1 %) of the dogs were considered normal by the owner between seizures (the inter-ictal phase). Of the remaining dogs, five of seven were on phenobarbital and showed behavioural changes most consistent with effects of the antiepileptic medications, such as ataxia and sedation. One of the dogs on antiepileptic medications was reported to be restless and anxious in a way that it had not been previously, during the inter-ictal phase. The two dogs that were not on medication were both reported to be more apprehensive and irritated than before the seizures started.
Diagnostic work-up in the field
Most of the dogs diagnosed with epilepsy (35/37) presented to a veterinarian because of the seizures. The diagnostic evaluation included haematology and a serum biochemical profile (32/37), and further investigations performed for some of the dogs included cerebrospinal fluid (CSF) analysis (n = 1), magnetic resonance imaging (MRI) (n = 2), computed tomography (CT) (n = 1), and abdominal ultrasound (n = 5).
Six of 37 (16.2 %) dogs in this study had been treated for other diseases: sub aortic stenosis (n = 1; diagnosed as puppy and receiving treatment with a β-blocker), cranial cruciate ligament rupture (n = 3; receiving NSAIDs (nonsteroidal anti-inflammatory drugs) (for pain relief)), and hypothyroidism (n = 2; supplemented with levothyroxine). None of dogs diagnosed with epilepsy had sustained brain injuries resulting in loss of consciousness during their lifetime. None of the dogs for which information about the neonate period was available (n = 15) received intensive care or help from the breeder to survive the paediatric period.
Fourteen of the dogs were not on any antiepileptic medication at the time of data collection; because of infrequent seizures, newly diagnosed disease or the owners’ concern for potential side-effects of the antiepileptic treatment. Twenty-four dogs received phenobarbital, and five of these received add-on treatments: potassium bromide and levetiracetam (n = 1), potassium bromide (n = 3), or imepitoin (n = 1). The median time from seizure onset to initiation of antiepileptic drugs was 36 days (range: 1–730 days); 90 % of the dogs were on medication within 6 months from seizure onset. Serum phenobarbital levels were monitored in 15/24 (62.5 %) of the treated dogs. Following initiation of antiepileptic treatment, the seizure frequency decreased for 15/21 (71.4 %) of the dogs, but for 6/21 (28.6 %) the seizure frequency increased. Only 8/18 (44.4 %) dogs experienced less severe or shorter seizures after initiation of medical therapy (data was missing for remaining dogs due to short treatment time). The most common side effects of the antiepileptic drugs were polyphagia (7/21), polydipsia (7/21), exercise intolerance (7/21), reduced ability to focus (6/21), sedation (6/21), and ataxia (5/21). Reduced working ability was reported as a side effect by the owners of 8/21 (38.1 %) of the dogs. Seven of the treated dogs reported no side effects of antiepileptic medications. Only six dogs were administered additional rectal diazepam, during seizures. Three owners gave their dogs dietary supplements such as cobalamin and magnesium. Seven dogs were neutered after the onset of seizures, but none of these experienced reduced seizure frequency or intensity after the procedure. Three dogs were euthanized before the time-period of 4 months, due to severe seizures, poor seizure control and severe side effects of the anti-epileptic medication. One of these owners, with small children in the household, also reported that they were afraid of their dog’s aggressive behaviour during the post-ictal phase.
Serum from 29 dogs was analysed, for the remaining 9 cases the serum was unavailable for analysis. Seven of the dogs had increased values of urea, Crea, and Glob, and 12 of the dogs had an increased ALP activity. All remaining serum biochemical values were within the reference intervals provided by the laboratory.
Family history and pedigree
All of the 37 dogs in this study had close relatives (siblings, parents, offspring) or second-degree relatives (grandparents, cousins) with epilepsy and 22/37 (59.5 %) of the dogs shared one common ancestor. This dog was used extensively for breeding during 1992–1997, fathering almost 300 offspring and grandfathering 850 in Sweden only.