Issue Description Granulomatous meningoencephalitis (GME) is an
inflammatory disease of the central nervous system (CNS) of dogs and,
rarely, cats. It is a form of meningoencephalitis. GME is likely
second only to encephalitis caused by canine distemper virus as the
most common cause of inflammatory disease of the canine central
nervous system. Other Names Granulomatous Meningoencephalitis
Types of GME
Disseminated - This is a diffuse disease
throughout the CNS. It was previously known as inflammatory
reticulosis. There is an accumulation of mononuclear cells and
neutrophils around the blood vessels (perivascular) of the CNS.
Meningitis is seen with this form of GME and causes fever and neck
pain. It has an acute progression over a few weeks. Symptoms include
incoordination, nystagmus, head tilt, seizures, and depression.
Focal - The disease presents as a granuloma, which mimics a tumor.
It usually is found in the cerebrum or cerebellopontine angle.
Symptoms may be acute or develop slowly over several months and depend
on the location of the lesion.
Ocular - This is an uncommon form of GME and is characterized by
sudden blindness caused by optic neuritis. The disease is bilateral.
Ocular GME is considered to be an extension of CNS disease. The blood
vessels of the posterior segment of the eye and anterior uvea have the
same infiltrates of inflammatory cells as the intracranial vessels.
Uveitis, retinal detachment, and secondary glaucoma may be seen.
Diagnosis and Treatment Cerebrospinal fluid (CSF) analysis shows a
large number of white blood cells. Typically small mature lymphocytes
are the majority of cells seen, with monocytes and neutrophils making
up the rest. A CT scan or MRI will show patchy, diffuse, or multifocal
lesions. Treatment is with immunosuppressive drugs such as
corticosteroids, azathioprine, and cyclophosphamide. Procarbazine,
cyclosporine, and cytosine arabinoside have also been used
successfully. Treatment with radiation therapy for focal GME gives the
longest periods of remission. The condition is rarely cured. The
animal usually dies within a few months.
Other Types of Noninfectious
Steroid-responsive meningoencephalitis is
any noninfectious meningoencephalitis that responds well to
corticosteroids and usually has an excellent prognosis. This could
represent mild forms of GME or PDE, but there are two separate
conditions recognized also.
Steroid-responsive meningitis/arteritis , also known as
necrotizing vasculitis, is seen most commonly in Beagles, Boxers,
Bernese Mountain Dogs, and German Shorthaired Pointers younger than
two years of age. Many cases have fever, loss of appetite, and severe
neck pain without other neurologic symptoms, although longterm cases
may have incoordination and limb weakness or paralysis. CSF analysis
shows predominantly neutrophils. In Beagles this condition is also
known as Beagle pain syndrome.
Eosinophilic meningoencephalomyelitis is seen mainly in Golden
Retrievers. CSF analysis shows predominantly eosinophils.
An acute progressive pyogranulomatous meningoencephalomyelitis is
seen in mature Pointer dogs. There is monocytic and neutrophilic
infiltration of the leptomeninges. Symptoms include incoordination,
reluctance to move, and neck rigidity.
Pug Dog encephalitis Pug Dog encephalitis (PDE) is an idiopathic
inflammatory disease primarily affecting the prosencephalon (forebrain
and thalamus). It is also known as necrotizing meningoencephalitis.
The disease may be inherited in Pugs and Maltese. It differs in
pathology from GME by more tissue breakdown and increased eosinophils.
CSF analysis is also unique among inflammatory CNS diseases in dogs in
that the cells are predominately lymphocytes instead of a mixed
population of mononuclear cells. In Maltese and Pugs there is
extensive necrosis and inflammation of the gray matter of the cerebrum
and subcortical white matter. The most common early symptoms are
related to forebrain disease and include seizures and dementia, and
later circling, head tilt, and blindness with normal pupillary light
reflexs may be seen. Corticosteroids may improve symptoms, but the dog
almost always dies from the disease.