Facial neuropathy in dogs and cats: 95 cases (1975-1985)

The medical records of 79 dogs and 16 cats admitted to the New York State College of Veterinary Medicine between January 1975 and October 1985 with facial nerve dysfunction were reviewed. In 31 dogs and 8 cats, facial neuropathy was the only abnormal finding. In 48 dogs and 8 cats, the clinical findings most often noted in the records in addition to facial neuropathy were vestibular signs. Facial neuropathy appeared unassociated with gender or right vs left sides in both dogs and cats, or with hypothyroidism in dogs. Facial neuropathy was associated with increased age, with certain breeds in both dogs and cats, and with otitis media/interna and keratoconjunctivitis sicca in dogs. Causes of facial nerve dysfunction in dogs and cats included surgical and nonsurgical trauma, neoplasia, and otitis media/interna. Facial neuropathy was judged to be idiopathic in 74.7% of dogs and 25% of cats.     

MAGNETIC RESONANCE IMAGING OF THE INTRATEMPORAL FACIAL NERVE IN IDIOPATHIC FACIAL PARALYSIS IN THE DOG

The most common cause of peripheral facial nerve paralysis in dogs, in the absence of otitis media, is thought to be idiopathic. Gadolinium-enhanced (Gd) magnetic resonance (MR) imaging has been used to study peripheral facial weakness in humans with a wide variety of disorders, including Bell's palsy, the clinical equivalent of idiopathic facial nerve paralysis in dogs. Gd-MR imaging may be useful to demonstrate abnormal enhancement of the intratemporal facial nerve. The aim of this study was to define the role of the Gd-MR imaging in dogs with idiopathic facial nerve paralysis, with regard to pattern of enhancement, and to search for prognostic information. Six dogs with peripheral facial nerve paralysis, followed between 2003 and 2005, were studied. Physical and neurologic examinations, as well as clinical tests, were performed, including routine hematology, serum biochemistry, thyroid screening, cerebrospinal fluid analysis, and MR imaging. The time interval between the onset of the clinical signs, the progress of the disease, and the final recovery was noted in each dog. The following four intratemporal segments of the facial nerve were analyzed: internal acoustic meatus, labyrinthine segment/geniculate ganglion, tympanic segment, and mastoid segment. Along its length, contrast enhancement was found in four dogs. In this group, contrast enhancement of the facial nerve was found in all segments of two dogs, in three segments of one dog, and in one segment of the other dog. In the four dogs with enhancement, one recovered completely in 8 weeks and three have not recovered completely. The two dogs without evidence of enhancement recovered completely in an average time of 4 weeks.     

Electrically induced blink reflex and facial motor nerve stimulation in beagles

Electrophysiologic assessment of the blink reflex test and the muscle-evoked potentials evoked by stimulation of the facial nerve were performed in 15 healthy adult Beagles before and after supraorbital (trigeminal) and facial anesthetic nerve blocks performed by lidocaine injections. Unilateral electrical stimulation of the supraorbital nerve elicited 2 ipsilateral (R1 and R2) and a contralateral (Rc) reflex muscle potential in orbicularis oculi muscles. Electrical stimulation of the facial nerve elicited 2 muscle potentials (a direct response [D] and a reflex faciofacial response [RF]) in the ipsilateral orbicularis oculi muscle. Anesthetic block of the left supraorbital nerve resulted in bilateral lack of responses upon left supraorbital nerve stimulation, but normal responses in right and left orbicularis oculi muscles upon right supraorbital stimulation. Right facial anesthetic block produced lack of responses in the right orbicularis oculi muscle regardless the side of supraorbital nerve stimulation. Results of this study demonstrate that the blink reflex can be electrically elicited and assessed in dogs. Reference values for the blink reflex responses and for the muscle potentials evoked by direct facial nerve stimulation in dogs are provided. The potential usefulness of the electrically elicited blink reflex test in the diagnosis of peripheral facial and trigeminal dysfunction in dogs was demonstrated.     

Laryngeal Paralysis-Polyneuropathy Complex in Young Rottweilers

Five Rottweiler puppies from 3 unrelated litters developed inspiratory stridor at 11–13 weeks of age. Physical examination disclosed tetraparesis in all dogs, and bilateral lenticular cataracts in 4 dogs. Laryngeal examination under light anesthesia showed laryngeal paralysis in all dogs. Electrodiagnostic testing revealed denervation potentials in the distal appendicular muscles of 4 dogs tested and in the intrinsic laryngeal muscles of 2 dogs tested. Motor nerve conduction velocity was slightly low in 1 dog. Neurogenic muscular atrophy was found in distal appendicular muscles (n = 3) and intrinsic laryngeal muscles (n = 2), and degenerative changes were found in peripheral nerves (n = 3) and recurrent laryngeal nerves (n = 2). No abnormalities were detected in the spinal cord, spinal nerve roots, or ganglia of 3 dogs autopsied. The clinical, electrophysiologic, and histopathologic findings support a diagnosis of polyneuropathy and resemble the finding reported in young Dalmatians. Young dogs with laryngeal paralysis should be evaluated neurologically to rule out a more generalized polyneuropathy. The condition is suspected to be hereditary in nature and the prognosis is poor.     

Asymmetrical focal neurological deficits in dogs and cats with naturally occurring tick paralysis (Ixodes holocyclus): 27 cases (1999-2006)

OBJECTIVE: To describe basic epidemiological features, clinical characteristics and outcomes of asymmetrical focal neurological deficits identified in dogs and cats with naturally occurring tick paralysis (Ixodes holocyclus). DESIGN: A retrospective study. PROCEDURE: Computer records were reviewed for all dogs and cats treated for tick paralysis between July 1999 and June 2006 at a suburban veterinary hospital in Newcastle, New South Wales. RESULTS: Neurological deficits were identified in 17/197 dogs and 10/89 cats and included unilateral facial paralysis (14 dogs; 2 cats), anisocoria (4 dogs; 7 cats), unilateral loss of the cutaneous trunci reflex (1 dog; 1 cat) and Horner's syndrome in 2 cats with anisocoria. Occurrence of deficits was not linked to season, severity of tick paralysis, breed, age, sex or body weight. With facial paralysis and anisocoria, the site of tick attachment was invariably on the head or neck and always ipsilateral to the facial paralysis. By contrast, with anisocoria alone, no consistent relationship was noted between any one pupillary dimension and the side of tick attachment. With cutaneous trunci deficits the site of tick attachment was the ipsilateral caudal axilla. Compared with recovery times from generalised signs of tick paralysis, those for facial paralysis were significantly longer (days to weeks; P < 0.001), those for anisocoria showed no significant difference (P = 0.25) and those for cutaneous trunci deficits lagged by 6 and 7 days. CONCLUSIONS: Asymmetrical focal neurological deficits are a consistent finding in a proportion of dogs and cats with naturally occurring tick paralysis due to I. holocylcus.     

Insulinoma and Subclinical Peripheral Neuropathy in Two Dogs

Two dogs with diffuse, subclinical polyneuropathy associated with insulinoma are reported. Seizures were the dominant sign of central nervous system disease. One dog had clinical signs of facial nerve paralysis. Lesions in selected appendicular and cranial nerves included a mixture of demyelination, remyelination, and axonal degeneration. The incidence (range: 18-47%) of these changes far exceeded that of comparable nerves from six control dogs (range 0-11%). Myopathic and electrodiagnostic findings were compatible with the nerve changes.     

Congenital unilateral facial nerve paralysis in a Warmblood filly

A 17-month-old Warmblood filly was referred to our clinic for evaluation of congenital facial nerve (FN) paralysis. Clinical examination revealed a right-sided facial paralysis with mild masticatory muscle atrophy, mild dysphagia and exposure keratitis. Apart from the FN deficits, neurological examination of the remaining cranial nerves showed no abnormalities. Magnetic resonance imaging (MRI) examination using a 3.0 Tesla scanner showed that in comparison to the left FN, the intracranial section of the right FN between the pons and internal acoustic canal was thinner, whereas it appeared indistinct and thickened within the internal acoustic canal and facial canal. Signs of meningitis or encephalitis were not present on MRI. Cerebrospinal fluid analysis showed mild pleocytosis. The owner of the filly requested euthanasia due to the guarded prognosis. At necropsy, the intracranial section of the right FN was macroscopically thinner than the left side and within the facial canal, a 5 mm tissue stump could be identified with an absent extracranial part of the right FN. Histological examination of the brain stem showed different architecture of the left and right motor nuclei of the FN: in the left nucleus, motor neurons of a normal size and well stainable Nissl bodies were present, whereas in the right nucleus, neurons with Nissl bodies were decreased in number and size. Further, a cytoplasmic rich cell population with a nucleus size compatible with normal neurons was present. These cells were suspected to be atrophic neurons. The tissue stump within the facial canal was histologically identified as connective tissue. Unilateral malformation of the FN has not previously been described in the horse. This filly showed a right-sided, intracranial hypoplasia accompanied by an extracranial aplasia of the FN causing complete, congenital facial nerve paralysis, which corresponded to a difference in the architecture of the affected motor nucleus of the FN.     

Acute idiopathic polyneuropathy in the dog

From among a large group of dogs with acute tetraparesis, we identified 10 dogs with a distinct peripheral nerve disorder. Prior to the onset of signs, all of the dogs had been healthy, and none was known to have been exposed to a neurotoxin or raccoon bite. Weakness, with hypoactive or absent segmental reflexes, became progressively worse for 1 to 21 days. Results of electromyography and nerve conduction studies invariably were compatible with a diagnosis of polyneuropathy that predominantly affected proximal nerve segments. Appearance of nerve biopsy specimens and the short time course for functional recovery suggested a demyelinative component to the disorder. The extent of recovery was variable but often rapid and complete in dogs that did not succumb to complications in the early period. Corticosteroid therapy did not demonstrably influence the outcome. This acute idiopathic polyneuropathy in the dog shares many clinical and pathologic features with idiopathic polyradiculoneuritis (Coonhound paralysis).     

Total Ear Canal Ablation Combined with Lateral Bulla Osteotomy for End-Stage Otitis in Dogs Results in Thirty Dogs

Thirty dogs with end-stage otitis were treated by either unilateral or bilateral total ear canal ablation and lateral bulla osteotomy. Otitis was considered end stage when the horizontal ear canal was collapsed, stenotic, or occluded in conjunction with chronic infection of the external and middle ear. The dogs were evaluated clinically and radiographically for 4 to 63 months. The frequency of scratching, head shaking, aural drainage, and para-aural fistulation was significantly decreased. Abnormal ear carriage and head tilt were not changed. The results in 23 dogs were graded as excellent or improved. One dog died of intraoperative hemorrhage. Complications during the period from suture removal to follow-up included para-aural fistulation (3 dogs), facial nerve paralysis (5 dogs), and head tilt (3 dogs).     

Trigeminal neuropathy in dogs: a retrospective study of 29 cases (1991-2000)

The medical records of 29 dogs unable to close their mouths due to flaccid paralysis or paresis of the muscles innervated by the mandibular branch of the trigeminal nerve, were reviewed. Idiopathic trigeminal neuropathy was diagnosed in 26 dogs based on complete resolution of clinical signs and lack of any long-term neurological disease. Of these dogs, golden retrievers were overrepresented. No age, sex, or seasonal predispositions were identified. Trigeminal sensory innervation deficits were observed in 35% (9/26), facial nerve deficits were observed in 8% (2/26), and Horner's syndrome was observed in 8% (2/26) of dogs. Electromyographic examination of the muscles of mastication revealed abnormalities in seven of nine dogs. Results of cerebrospinal fluid analysis were abnormal in seven of eight dogs. Corticosteroid therapy did not affect the clinical course of the disease. Mean time to recovery was 22 days. Lymphosarcoma, Neospora caninum infection, and severe polyneuritis of unknown origin were diagnosed in three of 29 dogs at necropsy.     

Electrophysiological evaluation of traumatic forelimb paralysis of the dog

The results of clinical neurological, electromyographic and electroneurographic examinations in 26 dogs with traumatic forelimb paralysis are presented. The results of neurological examination varied considerably among the cases. Electromyographic evidence of denervation in the epaxial muscles was observed in 22 dogs. A post ganglionic dorsal root lesion was diagnosed in 14 cases by the presence of an evoked sensory nerve action potential in association with loss of conscious pain perception in the appropriate area. Motor nerve studies in the ulnar nerve were not helpful in discriminating root lesions from spinal nerve involvement. It was concluded that electromyographic examination of the ipsilateral epaxial muscles under general anaesthesia is essential for the detection of root involvement. Sensory conduction studies in the radial nerve are indicated if conscious pain perception is absent in the fifth digit. Motor and sensory conduction studies of the ulnar nerve system seldom provide additional diagnostic information seldom provide additional diagnostic information. The absence of electrophysiological signs of root involvement does not exclude a post ganglionic dorsal root lesion.     

Multimodal therapy including electroacupuncture for the treatment of facial nerve paralysis in a horse

This Case Report describes a 5‐year‐old Standardbred gelding that was referred to the Equine Hospital of ONIRIS Veterinary School of Nantes, France for a surgical procedure under general anaesthesia. Anaesthesia was induced and maintained intravenously and the horse was placed in left lateral recumbency with a padded halter. On post operative Day 1, a post anaesthetic distal facial nerve branch paresis was diagnosed based on clinical signs. The horse was discharged on post operative Day 2 with medical treatment based on anti‐inflammatory drug administration locally and systemically. The horse was re‐examined 2 weeks after the surgery; the left partial facial paralysis was still present and associated with amyotrophy of the muscles supplied by the buccal branches of the facial nerve. In accordance with the owner, the horse was hospitalised to start an electrostimulation treatment. The horse was treated every day for the first 4 days, then every 2 or 3 days during the following 3 weeks, for a total of 11 sessions. At the end of the second week of treatment, the horse was able to normally prehend the food and atrophy seemed reduced. The horse was discharged from hospitalisation at the end of the third week of treatment with specific recommendations. One month after discharge from the hospital just a slight asymmetry could be noticed at rest. Six months later, the training season began and the horse was able to perform. Facial paralysis due to nerve compression is a well‐known complication of anaesthesia. Gradual recovery of function over the weeks of treatment suggests that electroacupuncture may promote recovery and may hasten time of recovery.     

Distal denervating disease: a degenerative neuropathy of the distal motor axon in dogs

A group of ten dogs affected by an apparently identical denervating disease, is described. There was no breed or age predisposition but females were preferentially affected (70%). The rate of onset of signs was variable from a week to greater than 1 month. Quadriparesis was present to varying severities and in two dogs the head and neck could not be supported. Mastication, swallowing, respiration and bladder function were unimpaired. Pain sensation was normal, tone was usually decreased and the local limb reflexes depressed or absent. Muscle atrophy was often prominent. All cases bar one recovered but another dog was also destroyed. Electrophysiology revealed diffuse spontaneous activity in the muscles and the motor nerve conduction velocities were at the lower end of or just below the normal range. The evoked muscle potentials were reduced in amplitude. Sensory nerve potentials were normal. The pathology showed a degeneration of the distal intramuscular axons with collateral axonal sprouting. The muscle changes were typical of neurogenic atrophy. The disease has been called distal denervating disease (DDD) until the precise aetiology can be determined.     

Total Ear Canal Ablation Clinical Results in the Dog and Cat

The clinical results of 39 consecutive ear ablations (in 28 dogs and three cats) performed over a 15-year period were reviewed. Indications for ear canal ablation included hyperplastic tissue stenosis of the horizontal ear canal (23), failed lateral ear resections (13), and horizontal ear canal neoplasms (3). Ear ablation was successful in alleviating persistent signs of otitis in eight of 15 dogs with horizontal ear canal stenosis due to hyperplastic tissue, seven of 10 dogs with unsuccessful lateral ear resections, and two of five animals (three cats and two dogs) with horizontal ear canal neoplasms (follow-up time periods greater than 5 months). Surgical complications occurred following 82% of the ablations; wound infections (41%) and facial nerve damage (36%) were most common. Local wound and antibiotic therapy successfully treated prolonged drainage following ablation in five of nine dogs. Bulla osteotomy and drainage were successful in the treatment of three dogs (four ears) that were unresponsive to medical therapy with postoperative ear fistula following ablation, one of two dogs with prolonged ear drainage following ablation for failed lateral ear resection, and one dog with recurrence of signs of inner ear disease following ablation (follow-up period, 1 month to 4 years; mean, 3.4 years). Facial nerve damage caused by ablation was transient in nine of 14 ears, with most deficits returning to normal within 2 weeks.     

Otopathy secondary to trigeminal schwannoma in a Quarter Horse

Otitis media secondary to trigeminal nerve (CN-V) paralysis is described in dogs and humans but not in horses. An 18-month-old Quarter Horse colt was presented with history of mastication difficulties and a nonhealing corneal ulcer. Clinical findings were consistent with paralysis of the right CN-V. Computed tomography imaging showed otopathy media and a mass at the root of the CN-V. The colt was euthanised due to poor prognosis. Post-mortem magnetic resonance imaging showed enlargement of the right CN-V which was slightly hyperintense on T2W. Histopathology of the mass revealed fusiform tumoural cells, positive on vimentin- and S100 immunohistochemistry, consistent with a schwannoma. Otitis media was presumed secondary to CN-V paralysis and denervation of the right tensor veli palatini muscle involved in opening of the Eustachian tube. This is the first case of trigeminal schwannoma and secondary otopathy media described in a horse, which highlights the importance of imaging in investigating trigeminal nerve paralysis.     

CT AND MRI FEATURES OF CAROTID BODY PARAGANGLIOMAS IN 16 DOGS

Carotid body tumors (paragangliomas) arise from chemoreceptors located at the carotid bifurcation. In imaging studies, this neoplasm may be confused with other neck neoplasms such as thyroid carcinoma. The purpose of this retrospective, cross‐sectional study was to describe computed tomographic (CT) and magnetic resonance imaging (MRI) characteristics of confirmed carotid body tumors in a multi‐institutional sample of dogs. A total of 16 dogs met inclusion criteria (14 examined using CT and two with MRI). The most common reason for imaging was a palpable cervical mass or respiratory signs (i.e., dyspnea or increased respiratory noises). The most commonly affected breed was Boston terrier (n = 5). Dogs were predominantly male castrated (n = 10) and the median age was 9 years [range 3–14.5]. Most tumors appeared as a large mass centered at the carotid bifurcation, with poor margination in six dogs and discrete margins in ten dogs. Masses were iso‐ to hypoattenuating to adjacent muscles in CT images and hyperintense to muscles in T1‐ and T2‐weighted MRI. For both CT and MRI, masses typically showed strong and heterogeneous contrast enhancement. There was invasion into the adjacent structures in 9/16 dogs. In six of these nine dogs, the basilar portion of the skull was affected. The external carotid artery was entrapped in seven dogs. There was invasion into the internal jugular vein in three dogs, and into the external jugular, maxillary, and linguo‐facial veins in one dog. Imaging characteristics helped explain some clinical presentations such as breathing difficulties, Horner's syndrome, head tilt, or facial nerve paralysis.     

Treatment of Age‐Related Hearing Loss in Dogs with the Vibrant Soundbridge Middle Ear Implant: Short‐Term Results in 3 Dogs

Background: Age‐related hearing loss (ARHL), or presbycusis, is the most common form of acquired hearing loss in dogs. Middle ear implants have been used successfully in people with ARHL who cannot benefit from conventional hearing aids. Hypothesis: Audibility improves in dogs with ARHL after implantation of the Vibrant Soundbridge (VSB) middle ear implant. Animals: Three Beagle dogs with ARHL, mean age 11.1 years. Methods: The dogs were assessed pre‐ and postoperatively by brainstem‐evoked response audiometry (BERA), otoscopy, and computed tomography scans of the ears. A VSB middle ear implant was implanted unilaterally. Three months later the functionality of the implants was assessed by auditory steady‐state responses (ASSRs), after which the dogs were euthanized for histopathological examination. Results: The VSB was implanted successfully in all dogs. Recovery from surgery was uneventful, except for transient facial nerve paralysis in 2 dogs. ASSRs showed that hearing improved after activation of the implants with a mean of 20.7, 13, and 16.3 dB at 1, 2, and 4 kHz, respectively. The implantation procedure did not affect residual hearing (with inactive implants) as measured by BERA. Conclusions and Clinical Importance: Implantation of the VSB resulted in lower ASSR thresholds, but only at the higher gain settings of the audioprocessor. As in humans, a more powerful audioprocessor is required to treat sensorineural hearing loss exceeding 20 dB in dogs. A substantial improvement in patient‐owner communication will have to be demonstrated in future studies before the procedure can be recommended in clinical practice.     

Otitis media‐interna and secondary meningitis associated with Corynebacterium pseudotuberculosis infection in a horse

A one‐year‐old Thoroughbred colt was evaluated because of facial nerve paralysis, ataxia and fever. Neurological evaluation found the colt to be obtunded and grade 3/5 ataxic in all 4 limbs. Right‐sided facial nerve paralysis was present and a large, deep corneal ulcer noted in the right eye. Signs of vestibular disease were also present, including circling towards the right and horizontal nystagmus. A complete blood count showed mild leucocytosis, neutrophilia and hyperfibrinogenaemia. A computed tomography (CT) examination of the skull was performed under general anaesthesia and a diagnosis of right sided otitis media‐interna was made. Culture of fluid taken from the middle ear and cerebrospinal fluid collected from the atlanto‐occipital site yielded pure growth of Corynebacterium pseudotuberculosis. Initial therapy consisted of antimicrobial treatment with cefotaxime and anti‐inflammatory treatment with flunixin meglumine. Six days after initiating treatment, the colt developed Clostridium difficile associated colitis. The colitis resolved with supportive care and the colt was discharged from the hospital receiving chloramphenicol. Eight months later, the colt continued to be mildly ataxic (grade 1/5), with a slight head tilt and facial nerve paralysis. To the authors' knowledge, this is the first reported case of otitis media‐interna due to C. pseudotuberculosis in the horse.     

Sound signature for identification of tracheal collapse and laryngeal paralysis in dogs

The aims of this study were to investigate whether upper airway sounds of dogs with laryngeal paralysis and tracheal collapse have distinct sound characteristics, compared with unaffected dogs. The sounds of 5 dogs with laryngeal paralysis and 5 dogs with tracheal collapse were recorded. Honking sound appeared as predominant clinical signs in dogs with tracheal collapse. Laryngeal stridors appeared as predominant clinical signs in dogs with experimentally produced laryngeal paralysis by resection of laryngeal nerve, in which two types of stridor, I and II, were recorded. All these sounds were analyzed using sound spectrogam analysis. There were significant differences in duration (sec), intensity (dB), pitch (Hz), first formant (Hz), second formant (Hz), third formant (Hz), fourth formant (Hz) of sounds between the normal bark and two types of stridor or honking sound, indicating that the sound analysis might be a useful diagnostic modality for dogs with tracheal collapse and laryngeal paralysis.     

Chronic Otitis Externa and Otitis Media Treated by Total Ear Canal Ablation and Ventral Bulla Osteotomy in Thirteen Dogs

Ventral bulla osteotomy was combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media in 13 dogs (14 ears) that had been refractory to medical and surgical treatments. Resolution of disease occurred in 11 dogs (12 ears). One dog with unilateral disease underwent a second operation before achieving a good result. One dog was euthanatized for persistent unilateral disease after three surgical procedures. The recurrence of disease in these two dogs (15%) was associated with remnants of ear canal integument within the osseous horizontal canal or tympanic bulla. Facial paralysis occurred in four dogs (31%) and there were no complications in eight dogs (62%). This technique shows no advantage over lateral bulla osteotomy combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media.