Ganglioradiculitis (Sensory Neuronopathy) in a Dog: Clinical, Morphologic, and Immunohistochemical Findings

A 9-year-old Labrador Retriever was diagnosed with ganglioradiculitis (sensory neuronopathy). This idiopathic disease of mature dogs is characterized by a profound loss of sensory nerve function due to mononuclear inflammatory infiltration of peripheral ganglia and spinal nerve roots, with destruction of sensory neurons. Immunohistochemistry demonstrates that the infiltrating cells are primarily T lymphocytes and that immunoglobulins are not present on the cell membranes of affected neurons. The pathogenesis of ganglioradiculitis remains unclear, but the evidence points to a cell-mediated immune mechanism.

Acute lower motor neuron tetraparesis

Flaccid nonambulatory tetraparesis or tetraplegia is an infrequent neurologic presentation; it is characteristic of neuromuscular disease (lower motor neuron [LMN] disease) rather than spinal cord disease. Paresis beginning in the pelvic limbs and progressing to the thoracic limbs resulting in flaccid tetraparesis or tetraplegia within 24 to 72 hours is a common presentation of peripheral nerve or neuromuscular junction disease. Complete body flaccidity develops with severe decrease or complete loss of spinal reflexes in pelvic and thoracic limbs. Animals with acute generalized LMN tetraparesis commonly show severe motor dysfunction in all limbs and severe generalized weakness in all muscles.

Trigeminal and polyradiculoneuritis in a dog presenting with masticatory muscle atrophy and Horner's syndrome

A 9-year-old, spayed female, Airedale Terrier was euthanatized and necropsied after a progressive clinical course that included Horner's syndrome of the left eye and unilateral atrophy of the masticatory muscles. Although gross lesions were limited, a polyradiculoneuritis and ganglionitis that was most severe in the trigeminal nerves and ganglia were confirmed histologically. The inflammatory infiltrate consisted predominantly of macrophages and B and T lymphocytes that were phenotypically confirmed by immunostaining. Horner's syndrome was the result of damage to postganglionic sympathetic fibers that were incorporated in segments of the inflamed trigeminal nerve and its ophthalmic branch. Histologically, the character and distribution of the inflammation was similar to previously described syndromes of suspected immune-mediated etiology in humans and animals.

Suspected post-vaccinal acute polyradiculoneuritis in a puppy

A 4-month-old German shepherd puppy developed hindquarter weakness after vaccination with a multivalent vaccine. This is suggestive of post-vaccinal polyradiculoneuritis. To date, only 1 similar case has been reported, which may be due to the under-reporting of suspected adverse drug reactions.

Sensory polyganglioradiculoneuritis in a dog

Generalized reduction of nociception and conscious and unconscious proprioception were found in an approximately eight-year-old, male, Maltese mixed-breed dog presented for difficulty prehending food and experiencing ataxia of three months duration. Results of needle electromyogram, motor nerve conduction velocity, and cerebrospinal fluid analysis were normal. A diagnosis of sensory polyneuropathy was suspected. No underlying cause could be determined. Neurological signs progressed to quadriparesis over the following four months despite treatment attempts with prednisone and procarbazine. Necropsy confirmed a sensory polyganglioradiculoneuritis, but no inciting cause could be established.

Electrophysiologic assessment of acute polyradiculoneuropathy in dogs: comparison with Guillain-Barré syndrome in people

Electrophysiologic investigations of motor and sensory nerve as well as ventral nerve root function were performed on 12 dogs with suspected acute canine polyradiculoneuropathy (ACP) at different stages and with different severity of disease. The most reliable electrophysiologic indicators of ACP were electromyographic changes (occurring in 100% of affected dogs), significantly decreased compound muscle action potential amplitudes (in 75, 90, and 100% of affected dogs at all sites along the sciatic/tibial, radial, and ulnar nerves, respectively), increased minimum F-wave latencies (67%), increased F ratios (92%), and decreased F-wave amplitudes (67%). These findings suggest that ACP represents a peripheral motor axonopathy, with demyelination and axonal involvement also occurring in ventral nerve roots. Evidence of peripheral demyelination was present in some dogs although it was overshadowed by the prominent axonopathy. ACP more closely resembles the acute axonal or intermediate forms of Guillain-Barré syndrome in people.

Paralytic illness resembling inflammatory polyradiculoneuropathy in a chimpanzee

An adult male chimpanzee housed in an outdoor corral with a group of other chimpanzees had an acute onset of ascending motor paresis that progressed to flaccid tetraplegia over 3 days. Tendon reflexes were weak, and CSF protein concentration was high. The chimpanzee regained normal mobility over several months. This chimpanzee's ascending, symmetrical, monophasic, flaccid paralytic illness, with albuminocytologic dissociation in CSF, and recovery following supportive treatment, was characteristic of inflammatory polyradiculoneuropathy, known as Guillain-Barré syndrome in human beings. Coonhound paralysis and experimentally induced allergic neuritis are the counterparts in dogs and laboratory animals, respectively, of the syndrome. In human beings, the syndrome is apparently immunologically mediated, as it is known to develop after bacterial and viral infections, vaccinations, and surgery or injury. The chimpanzee of this report had been given a rabies vaccination and had been treated for dental abscess 12 days prior to onset of signs, and had been inoculated with material containing neuronal antigens 20 years prior to onset of signs.

Neospora-induced congenital myelitis and polyradiculoneuritis in a one-month-old Holstein calf

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Seizures and other neurologic manifestations of allergy

Numerous disease entities affecting the nervous system can be attributed at least in part to immune responses. Neurons have been shown to have receptors from many of the vasoactive neurotransmitter and neuromodulator molecules first studied as mediators of inflammation and immediate hypersensitivity (Type 1 response). Immune responses have now been proven to affect CNS and peripheral neurons. In the diagnostic workup, consideration should be given to the possibility of immune-related causes for seizures and some other neurologic disorders.

Neuromuscular disease in a dog

Diffuse neuromuscular disease occurs sporadically in dogs. The most commonly reported diffuse neuromuscular diseases are polyradiculoneuritis (coonhound paralysis), tick paralysis, botulism, and myasthenia gravis (1,2,12). This clinical report describes an atypical presentation of a diffuse neuromuscular disease in a dog.

Canine protozoan polyradiculoneuritis

Four pups in a litter of eight Labrador Retrievers suddenly developed hind limb weakness. In three, paralysis ascended rapidly resulting in quadriplegia, cervical weakness, dysphagia and death. Postmortem examination revealed a severe polyradiculoneuritis in which roots, ganglia, and spinal and cranial nerves were heavily infiltrated by lymphocytes, plasma cells and macrophages and contained abundant protozoan pseudocysts. On sections of the brain and spinal cord protozoa were less frequent and appeared independent of the glial nodules which marked focal areas of necrosis. The organisms initially were thought to be Toxoplasma gondii, but this supposition was not supported by serological, immunocytochemical, or electron microscopic findings. Ultrastructurally the organisms resembled an unidentified sporozoan parasite, which has been reported in the CNS of dogs in Scandinavia. The inflamed spinal roots contained many degenerated and demyelinated axons. Electron microscopic studies indicated that the tachyzoite-like organisms, through their invasive and proliferative activities, brought about many of the degenerative changes in the Schwann cells and axons of the spinal roots and nerves.

Acute canine idiopathic polyneuropathy. A Guillain-Barré-like syndrome in dogs

We evaluated 14 previously healthy dogs with acute progressive flaccid quadriparesis and hyporeflexia. Electrophysiological and pathological features indicated varying degrees of motor-sensory polyneuropathy with some demyelination. Perivenular cellular infiltrations were present in roots of one autopsied case. Recovery was rapid and often complete in dogs that did not die from respiratory complications. Two dogs subsequently developed a chronic progressive course and two had a relapsing, corticosteroid-responsive course. Acute canine idiopathic polyneuropathy (ACIP) shares many features with the Guillain-Barré syndrome, and may be a naturally occurring model of the human disorder.

Coonhound paralysis. Further clinical studies and electron microscopic observations

Prior study of coonhound paralysis (CHP) revealed an acute polyradiculoneuritis in raccoon-hunting dogs with clinical and pathologic features resembling those of Guillain-Barré syndrome (GBS). In the present series of five cases, the clinical features were investigated with emphasis on electrodiagnostic and CSF findings, and pathologic changes were evaluated with both the light and electron microscope. The demonstration of motor nerve conduction delay and CSF albuminocytologic dissociation in affected dogs further supported the clinical similarity of CHP and GBS. As in GBS, affected roots and nerves contained mononuclear cell infiltrates, segmental myelin changes and axon degeneration. Despite these general pathologic similarities, the present study suggested that axon damage was a more consistent finding in CHP than in GBS. In contrast to ultrastructural findings in GBS, the demyelinating process in CHP did not appear dependent upon macrophages for its initiation. Swelling, separation and vesiculation of myelin occurred around axons of reduced diameter often in the absence of proximate macrophages. Macrophages, rather than initiating demyelination, appeared to be superimposed on existing damage. In this regard, the observed changes resembled those reported in galactocerebroside-induced EAN and sera-mediated in vivo demyelination.

Experimental coonhound paralysis: animal model of Guillain-Barré syndrome

Coonhound paralysis (CHP), a polyradiculoneuritis of dogs that resembles the human Guillain-Barré syndrome, was experimentally reproduced by inoculating a dog with raccoon saliva. The test animal was a coonhound that had previously sustained two naturally occurring attacks of CHP. Success in inducing the disease strengthened the notion that raccoon saliva contains the etiologic factor for CHP and that only specifically susceptible dogs are at risk of developing CHP when exposed to this factor.

Neuritis of the cauda equina, a chronic idiopathic polyradiculoneuritis in the horse

Four cases of neuritis of the cauda equina (NCE) were studied by light and electron microscopy. Examination of sacral intradural rootlets revealed inflammatory cell infiltrates and an array of myelinated fiber changes which included myelin stripping by invading mononuclear cells and macrophages, as well as splitting and vesiculation of myelin lamellae without obvious participation by leukocytes. More distally in the extradural roots, there was marked granulomatous inflammation, and demyelinative changes were overshadowed by widespread evidence of irreversible axon damage. In all cases, unusual crystalline inclusions appeared in the endoneurium and sheaths of the rootlets and fascicles. The changes in NCE were compared and contrasted with those observed in acute and chronic inflammatory demyelinative neuropathies.