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Hospital Veterinario J. Gri√Ī√°n
Mutxamel (Alicante-Spain)
Avda Alicante, 18 (Edificio JG)
03110-Mutxamel (Alicante-Spain)
Tfno: 96.5951897
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NEUROPAT√ćA DEL TRIG√ČMINO

DISEASES OF MASTICATION:
The trigeminal nerve give rise to the sensory nerves for the skin and structures of the eye, nose, mouth and face and the motor nerves to the muscles of mastication.
It consists of 3 major branches:
the ophthalmic nerve which is sensory to the structures of the orbit and skin of the dorsum of the nose;
the maxillary nerve which is sensory to the skin of the cheek, side of the nose, muzzle, mucous membrane of the nasopharynx, maxillary sinus, soft and hard palates and the teeth and gingiva of the upper jaw;
and , the mandibular nerve which is sensory to the remaining portions of the face and mouth and is motor to the muscles of mastication.
Diseases of the trigeminal nerve or the muscles of mastication are not uncommon and must be differentiated from one another.

Trigeminal neuritis (an immune disorder affecting the myelinated pathways in the trigeminal nerve) is usually transient, but can present as a significant problem.
The cardinal signs of trigeminal neuritis if a dropped jaw with the inability to close the mouth.
It affects adult dogs and cats with no breed or sex predilection. It must be differentiated from fracture or subluxation of the temporomandibular joint (evaluated by skull radiographs).
On pathologic examination, there is bilateral nonsuppurative neuritis of the trigeminal nerve.
As an idiopathic immune-related disorder, the condition will usually improve over 1-3 weeks.
On the other hand, methylprednisolone therapy may help reduce the severity of an attack.
Additional measures includes the use of antioxidant medications such as vitamin E and C, n-acetylcysteine and ginkgo biloba. These latter measures may help prevent reoccurrence of episodes, which are occasionally seen. Other measures including feeding liquified food and/or introduction of a PEG tubes to support nutrition while the neuritis slowly responses. Some have supported the patients nutrition by placing a wide rubber band around the mouth (which helps close the mouth) while the patient is allowed to eat.

Masseter and temporalis myositis is a chronic progressive which presents with acute exacerbations and remissions.
It is an auto-immune disease directed at the unique antigenic markers of the muscles innervated by the trigeminal nerve.
The cardinal signs of this myositis is the inability to open the jaw, which differentiates it from primary diseases of the trigeminal nerve.
In the acute phase, there is elevation of serum muscle enzymes (CPK, AST, LDH and aldolase).
On the CBC, there is often an elevation of eosinophils (giving the condition its names, eosinophilic myositis).
On the other hand, in the chronic phase, the amount of remaining muscle and, therefore, the amount of inflammation are reduced.
The diagnosis can be confirmed on muscle biopsy and determination of serum antibody titers to the 2M antigen.
The treatment of acute masseter-temporalis myositis is with immunosuppressive medication. We use oral prednisolone at 1 mg/kg/day divided into 2 or 3 doses for 1-2 weeks, followed by 0.5 mg/kg/day for 1-3 weeks.
There is no evidence to suggest that keeping patients on alternate day steroid therapy between attack will reduce the chances for progression. Here is another area where using dietary supplements might be useful. In the chronic phase, the jaw may be locked shut.
In these cases, it may be necessary to manually open the mouth under anesthesia. This may lead to fracture of the jaw. The hope is that, once the fibrosis is broken, the remaining muscle mass will allow enough function for the patient to be able to feed itself. The jaw must open about 1-1.5 inches for this to happen.

fuente: UNIVERSIDAD DE FLORIDA (USA)

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