Surgical treatments for seizure. Adaptability for dogs

Non-pharmacological treatment options for refractory epilepsy: an overview of human treatment modalities and their potential utility in dogs

Refractory epilepsy is a common disorder both in humans and dogs and treatment protocols are difficult to optimise. In humans, different non-pharmacological treatment modalities currently available include surgery, the ketogenic diet and neurostimulation. Surgery leads to freedom from seizures in 50-75% of patients, but requires strict patient selection. The ketogenic diet is indicated in severe childhood epilepsies, but efficacy is limited and long-term compliance can be problematic. In the past decade, various types of neurostimulation have emerged as promising treatment modalities for humans with refractory epilepsy. Currently, none of these treatment options are used in routine daily clinical practice to treat dogs with the condition. Since many dogs with poorly controlled seizures do not survive, the search for alternative treatment options for canine refractory epilepsy should be prioritised. This review provides an overview of non-pharmacological treatment options for human refractory epilepsy. The current knowledge and limitations of these treatments in canine refractory epilepsy is also discussed.

Electroencephalographic recordings in dogs suffering from idiopathic and symptomatic epilepsy: diagnostic value of interictal short time EEG protocols supplemented by two activation techniques

The diagnostic value of interictal short time electroencephalographic (EEG) recordings in epileptic dogs under general anaesthesia with propofol and the muscle relaxant rocuronium bromide was investigated. Two activation techniques, namely photic stimulation and hyperventilation, were evaluated for their potential to enhance the diagnostic validity of these recordings. Sixty-one dogs suffering from idiopathic epilepsy and 28 dogs suffering from symptomatic epilepsy were included. Electroencephalograms were recorded using five subdermal EEG electrodes (F3, F4, Cz, O1 and O2). All 89 EEGs were analysed visually and 61 were also evaluated quantitatively with fast Fourier transformation. Interictal paroxysmal epileptiform activity was found in 25% of idiopathic and in 29% of symptomatic epileptic dogs. Quantitative analysis of the EEGs (qEEGs) detected significant differences of frequency analysis in single reading points without any continuous changes of frequency bands. A comparison between healthy and affected brain hemispheres in seven dogs with focal lesions of one hemisphere did not show any significant differences in qEEG analysis. qEEG was not more sensitive than visual evaluation. Despite the use of activation techniques, the results showed that short time EEG recordings in epileptic dogs can detect interictal epileptic activity in less than one third of all seizuring dogs and is not a useful screening method.

Regional brain perfusion in epileptic dogs evaluated by technetium-99m-ethyl cysteinate dimer SPECT

We evaluated the feasibility of interictal single photon emission computed tomography (SPECT) to detect alterations in regional cerebral blood flow and neuronal activity in dogs with idiopathic epilepsy. Twelve dogs with idiopathic epilepsy underwent interictal technetium-99m-ethyl cysteinate dimer SPECT of the brain. Different cortical regions of interest (ROIs), 1 ROI at the cerebellum and 1 ROI at the subcortical area were evaluated by semiquantitative analysis and compared with a control group (18 dogs). Significant hypoperfusion (P = 0.02) was present in the subcortical area of epileptic dogs. This hypoperfusion was not associated with seizure frequency, age at onset of seizures, duration of epilepsy, or time since the last seizure. Interictal SPECT did not reveal cortical or cerebellar perfusion alterations. The subcortical area may play an important role in the pathophysiology of canine idiopathic epilepsy.

MAGNETIC RESONANCE IMAGING OF ACQUIRED TRIGEMINAL NERVE DISORDERS IN SIX DOGS

The medical records and magnetic resonance (MR) images of dogs with an acquired trigeminal nerve disorder were reviewed retrospectively. Trigeminal nerve dysfunction was present in six dogs with histologic confirmation of etiology. A histopathologic diagnosis of neuritis (n=2) or nerve sheath tumor (n=4) was made. Dogs with trigeminal neuritis had diffuse enlargement of the nerve without a mass lesion. These nerves were isointense to brain parenchyma on T1-weighted (T1W) precontrast images and proton-density-weighted (PDW) images and either isointense or hyperintense on T2-weighted (T2W) images. Dogs with a nerve sheath tumor had a solitary or lobulated mass with displacement of adjacent neuropil. Nerve sheath tumors were isointense to the brain parenchyma on T1W, T2W, and PDW images. All trigeminal nerve lesions enhanced following contrast medium administration. Atrophy of the temporalis and masseter muscles, with a characteristic increase in signal intensity on T1W images, were present in all dogs.

Pneumonia after intracranial surgery in dogs

OBJECTIVE

To determine factors associated with the occurrence of pneumonia after intracranial surgery in dogs.

STUDY DESIGN

Retrospective cohort study. Animals-Forty-nine client-owned dogs.

METHODS

The medical records of 49 dogs with space-occupying intracranial disease that underwent craniotomy were reviewed. Development of pneumonia after surgery was considered highly likely in 12 dogs (affected dogs) based on clinical signs, including acute dyspnea or coughing in association with typical radiographic findings or abnormal transtracheal wash results. Pneumonia was confirmed in 6 dogs based on necropsy findings. Affected dogs were compared with 37 dogs that did not develop pneumonia (unaffected dogs) subsequent to intracranial surgery. Based on the medical records of affected dogs, determinations were made regarding time between development of pneumonia and surgery, surgical procedure, intracranial lesion type, and intracranial lesion location. Risk factors examined for both affected and unaffected dogs included level of consciousness, body position during the postoperative recovery period, duration of anesthesia, occurrence of vomiting or regurgitation, presence of seizures, cranial nerve deficiencies, and the presence of megaesophagus before and after surgery. We also compared the feeding protocol after surgery for each group.

RESULTS

Pneumonia typically occurred within the first week after surgery (median, 6.5 days); however, this was variable (range, 1-96 days). Of the factors that were present within 24 hours before the clinical signs of pneumonia, vomiting or regurgitation and megaesophagus were found to be significant risk factors. Dogs that vomited or regurgitated were 2.71 times more likely to develop pneumonia than dogs that did not. Vomiting or regurgitation occurred in 63% of the dogs that developed pneumonia in this cohort. Dogs with megaesophagus were 9.25 times more likely to develop pneumonia than dogs without megaesophagus. Seven dogs with pneumonia died. Five of these 7 dogs appeared to have died as a direct sequel to pneumonia.

CONCLUSION

Dogs undergoing craniectomies for space-occupying intracranial disease may be at higher risk for development of pneumonia due to several factors, including vomiting, regurgitation, and megaesophagus.

Hemihyperaesthesia and hyperresponsiveness resembling central pain syndrome in a dog with a forebrain oligodendroglioma

A 4-year-old male Boxer was presented with neurological signs referable to a right forebrain lesion that was confirmed with computed tomography. Whilst characteristic signs of a unilateral forebrain lesion were observed, the dominant and striking finding was a right-sided hemisensory disturbance characterised by hyperaesthesia and hyperresponsiveness. Necropsy revealed a gelatinous mass confined to the right forebrain that was identified histologically as an oligodendroglioma. The lesion was centred on the internal capsule and involved ventral frontal and temporal lobes and the ventrolateral thalamus, including lateral and medial parts of the ventrocaudal nuclear region (ventrobasilar complex) of the thalamus. On clinical and neuroanatomical grounds, the case exhibited features in common with central pain syndrome in human patients with thalamic lesions. These included a somatosensory disorder of hyperaesthesia affecting an entire side of the head and body, behavioural manifestations consistent with spontaneous pain and a lesion involving the ventrobasilar complex. Of interest, the hemisensory abnormality was ipsilateral to the lesion, contrasting with central pain in humans, in which clinical signs are contralateral to analogous lesions. It is suggested that species-specific differences in spinal cord organisation of pain pathways, particularly the greater bilateral projection of nociceptive afferents to thalamic relay nuclei in carnivores, may account for this disparity. Notably, central pain is rare in human patients with brain tumours, even those affecting the thalamus, and this may also be the case in dogs.

Idiopathic epilepsy in dogs

Idiopathic epilepsy is a chronic condition characterized by recurrent seizures for which there is no identifiable cause. It is the most common neurologic disorder in the dog. This article discusses the diagnostic evaluation and rational treatment of dogs with recurrent seizures. Types of seizures, client education, choice of therapy, use of specific drugs, therapeutic monitoring, and nondrug treatments are reviewed.

Electroencephalography in dogs with epilepsy: similarities between human and canine findings

OBJECTIVES

To investigate the diagnostic value of electroencephalography (EEG) in dogs with epilepsy, applying human criteria for EEG abnormalities observed with this disorder.

MATERIAL AND METHODS

Twenty-six dogs with a clinically established diagnosis of epilepsy were investigated with electroencephalography (EEG) in order to evaluate the diagnostic yield of EEG in canine epilepsy.

RESULTS

Of 23 dogs with evaluable EEGs 15 (65%) demonstrated abnormal activity. The most common abnormalities were focal low frequency patterns without spikes (48%), followed by focal epileptiform activity (22%) and generalized epileptiform activity (17%). The distribution between focal and generalized activity were 73% and 27%, respectively. Consistency were demonstrated between the clinical- and the EEG-diagnosis in 13 dogs (87%). A relationship was demonstrated between the number of abnormal EEGs and the proximity of a seizure to the EEG examination.

CONCLUSION

A marked consistency was demonstrated between the clinical diagnosis of seizure type and the type of abnormalities observed in the EEG, thus indicating that EEG is a valuable diagnostic aid in confirming the diagnosis of epilepsy in dogs. EEG findings in dogs with epilepsy and humans with this disorder were markedly similar.

Idiopathic epilepsy

Idiopathic epilepsy is one of the most common and treatable neurologic diseases of small animals. The objectives of this article are to present a clinical overview and practical approach to its management. A review of terminology, epidemiologic issues, diagnosis, differential diagnosis, and general principles of treatment are presented.