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"I'll take neurology for 500" (Proceedings)

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Aug 01, 2010

Staphylococcus is a common cause of discospondylitis. Spinal epidural empyema (i.e. abcess) is most often associated with E. Coli, Bacteriodes spp and S. Intermedius.1 Thus, antibiotic choice should be targeted at these organisms when a bacterial infection is suspected. Cephalosporins and amoxicillin/clavulanic acid are both good choices. A fluoroquinolone may be used if a therapeutic response is not initially seen with the previous antibiotic choices. Fungal discospondylitis can be difficult to diagnosis, as a bacterial cause is typically suspected. Aspergillus tereus, Cladophialophora and Paecilomycosis may also cause discospondylitis. Coccidiomycosis can cause vertebral osteomyelitis. Fungal serology and often times biopsy and culture may be required to diagnose fungal infections of the spine. Itraconazole or voriconazole should be considered for fungal discospondylitis and osteomyelitis. While fluconazole is often used for CNS fungal infections because of its penetration in to CSF, it has little activity against Aspergillus.2

Thoracic limb lameness is often initially thought to be of orthopedic origin. Degenerative joint disease, tendon injury, neoplasia, trauma and less commonly osteomyelitis and joint infection encompass non neurological causes for lameness. Neurologic causes are commonly overlooked initially. Significant muscle atrophy, ataxia, horner's syndrome and CP deficits may suggest a neurologic cause for the lameness. Neoplasia (Peripheral nerve sheath tumor and lymphoma) not uncommonly affects the brachial plexus. Pain may or may not be present on palpation of the axilla. Lateralized disc herniations may cause thoracic limb lameness and are often painful. Radiographs of the affected limb and thorax can help identify neoplasia. Spinal MR imaging that includes the brachial plexus is helpful in differentiating disc disease from neoplasia. CSF analysis is important to evaluate for lymphoma and inflammatory CNS diseases. Amputation of the affected limb may be of benefit when peripheral nerve sheath tumors are present. However, good margins are often difficult to obtain in the brachial plexus. Thus, the high likelihood of recurrence makes amputation of questionable benefit when the tumor is quite proximal, at the level of the spinal canal. While radiation therapy is of benefit in peripheral nerve sheath tumors, anecdotally it is of limited benefit when the brachial plexus is involved. Loss of the ipsilateral cutaneous trunci reflex occurs with traumatic brachial plexus injuries, in which avulsion of the caudal brachial plexus occurs. The prognosis with brachial plexus injuries is poor. Traction injuries without avulsion may improve with time and rehabilitation therapy.

Horner's syndrome most commonly occurs with lesions of the middle ear or with a lesion from T1-T3. A partial horner's syndrome may be present with a lesion a T1. The occurrence of an acute C6-T2 myelopathy with concurrent horner's syndrome is commonly associated with fibrocartilaginous embolism and less commonly neoplasia.

Idiopathic cerebellitis (i.e. White Shaker Dog syndrome) occurs in small breed dogs of any coat color. Dogs classically present with tremors that worsen with movement. Cranial MR imaging is typically normal or may have very subtle changes in the cerebellum. CSF analysis typically identifies a mild pleocytosis. GME typically has a greater pleocytosis compared to idiopathic cerebellitis. However, at times GME can have a mild pleocytosis making differentiation difficult. The prognosis with idiopathic cerebellitis is typically good with immunosuppressive prednisone therapy. Dogs can often be tapered off of prednisone after a few months of therapy. Relapse can occur with premature withdrawal of prednisone therapy.

Anticonvulsant therapy for cats is often frustrating if phenobarbital is not successful. The use of potassium bromide is no longer recommended in cats due to the potential for asthma secondary to bromide therapy. Signs may resolve once bromide therapy is discontinued. The longer half life of diazepam in cats makes it a possible candidate for long term anticonvulsant therapy. However, the use of oral diazepam is limited due to the potential risk of severe liver disease in cats. Extensive studies regarding safety and efficacy of newer anticonvulsants in cats are lacking. Gabapentin may be used, however it has not been highly efficacious for seizures in small animals. Newer anticonvulsants such as levetiracetam 20 mg/kg PO TID and zonisamide 5-10 mg/kg PO SID in cats appear promising. Due to the limited number of studies and anecdotal experience (lower incidence of seizures in cats compared to dogs) care should be used when using these medications. Starting at the lower end of the dose range may be of benefit. Serial monitoring of the CBC and serum chemistry is recommended.