Page 1286 - Cote clinical veterinary advisor dogs and cats 4th
P. 1286

648   Meningoencephalitis of Unknown Origin


            ○   Brainstem signs: central vestibular disease   •  Histopathology (surgical biopsy or necropsy):   ○   Targeted whole blood concentrations,
              (head tilt, ataxia)               confirms GME or NE                   measured  1  week  after  initiation  of
  VetBooks.ir  Etiology and Pathophysiology    TREATMENT                           ○   Small size of many MUO patients may
                                                                                     therapy or dosage change: 800-1400 ng/
            ○   Meningitis: cervical pain
                                                                                     mL (peak), 400-600 ng/mL (trough)
           •  Cause is unknown; presumed autoimmune
            or immune mediated                Treatment Overview                     necessitate compounded formulations of
                                              Glucocorticoids are the benchmark of treat-
                                                                                     cyclosporine; commercially available liquid
           •  Attempts to identify an inciting infectious   ment. The choice of add-on therapy varies   formulation can be used (minimum dose
            cause have been unrewarding.      based on clinician preference, owner finances,   of  10  mg/kg  PO  q  12h  often  required
           •  Antibodies against neural elements (astro-  proximity to a hospital capable of administer-  to achieve therapeutic concentrations).
            cytes, glial fibrillary acidic protein) have been   ing chemotherapy, and owner health concerns   The  microemulsified  form  (Neoral/
            identified in serum and cerebrospinal fluid   (immune compromised/pregnant). Cytarabine,   cyclosporine modified) is recommended
            (CSF) of affected dogs.           cyclosporine,  procarbazine,  azathioprine,   over Sandimmune.
           •  Histopathology:  nonsuppurative,  mono-  mycophenolate mofetil, and radiation therapy   ○   Vaccines may be less effective in dogs
            nuclear cell infiltration in the brain and/or   have been used.          on  cyclosporine;  avoid  live  attenuated
                              +
            meninges, especially CD8  T lymphocytes in                               vaccines.
            GME                               Acute General Treatment            •  Procarbazine (Matulane, Alcami) 25-50 mg/
                                                                                     2
                                              •  Prednisone/prednisolone is initiated at antiin-  m  PO q 24h decreasing to q 48h dosing
            DIAGNOSIS                           flammatory dosages (e.g., 0.5-1 mg/kg PO q   after 1-3 months
                                                24h) pending infectious disease titers. Some   •  Azathioprine  2  mg/kg  PO  q  24h  for  2-4
           Diagnostic Overview                  advocate for immediate immunosuppression   weeks, then 2 mg/kg PO q 48h
           MUO should be considered based on signal-  (e.g., 2 mg/kg PO q 12h) after MRI and   •  Mycophenolate mofetil 20 mg/kg PO or IV
           ment and presenting clinical signs. Initial   CSF, based on the low positive yields from   q 12h, decrease to 10 mg/kg PO q 12h after
           diagnostics are performed to evaluate for other   infectious disease testing.  2-4 months, then 10 mg/kg PO q 24h for
           causes of neurologic disease. Diagnosis often   ○   If severity of neurologic signs at the   2-4 months, for a final dosing schedule of
           requires referral for MRI and CSF analysis.   time of diagnosis precludes the admin-  10 mg/kg PO q 48h. Capsules should not
           MRI or CSF can occasionally be normal,   istration of oral medications, consider   be opened, and the sodium enteric-coated
           highlighting the importance of a complete   drugs with IV formulations (dexa-  tablets should be avoided.
           diagnostic workup.                     methasone, methylprednisolone sodium   •  Tapering of medication dosages is contingent
                                                  succinate, cytarabine, mycophenolate     on the absence of recurrence of clinical signs.
           Differential Diagnosis                 mofetil).                      •  Lomustine 44-88 mg/m  PO q 6 weeks (p.
                                                                                                    2
           •  Infectious meningoencephalitis  •  Treat for common infectious diseases (doxy-  609). The use of live vaccines is discouraged.
            ○   Protozoal:  Toxoplasma gondii, Neospora   cycline 5-10 mg/kg PO q 12h, clindamycin   •  Radiation therapy 10 3-Gy treatments
              caninum                           15 mg/kg PO q 12h, fluconazole 5 mg/kg
            ○   Bacterial                       PO q 12h) while awaiting titer results.  Behavior/Exercise
            ○   Viral: canine distemper, rabies  •  Seizure  activity:  IV  benzodiazepines,  then   While on immunosuppressive therapy, com-
            ○   Tick-borne:  Ehrlichia canis, Anaplasma   initiate maintenance antiepileptic therapy   munal areas such as dog parks and boarding
              spp, Rickettsia rickettsii, Borrelia burg-  with parenteral formulation of phenobarbital   facilities should be avoided.
              dorferi, Babesia canis, Bartonella henselae  or levetiracetam. Levetiracetam tends to be
            ○   Fungal: Cryptococcus neoformans, Blasto-  preferred and has less effect on dog’s mental   Drug Interactions
              myces spp, Coccidioides immitis, Aspergillus   status than phenobarbital.  Cyclosporine, phenobarbital, and procarbazine
              spp, Histoplasma spp            •  Signs  of  elevated  intracranial  pressure   are metabolized by the  hepatic cytochrome
            ○   Other: Prototheca spp, Cuterebra  (depressed mental attitude/poor pupillary   P450  system;  they  alter  the  disposition  of
           •  Neoplasia                         light  reflexes):  mannitol  1 g/kg  IV  once   other drugs that depend on P450 enzymes for
           •  Vascular: ischemic or hemorrhagic stroke  or  3%  hypertonic  saline  4-6 mL/kg  IV     metabolism, necessitating a higher dose when
           •  Blindness (p. 123)                once.                            used in combination.
           Initial Database                   Chronic Treatment                  Possible Complications
           •  Neurologic exam (p 1136): to localize lesion  •  Prednisone/prednisolone: immunosuppressive   •  Glucocorticoid  side  effects  should  be
           •  Testing to rule out other causes for clinical   doses with a slow taper over the next year:   expected: polyuria, polydipsia, polyphagia,
            signs                               2 mg/kg PO q 12h for 3 days, then 1-1.5   ± others (e.g., hepatopathy, iatrogenic
            ○   CBC, serum chemistry, urinalysis  mg/kg  PO  q  12h  for  1-3  months,  then   hyperadrenocorticism)
            ○   Bile acids, preprandial and postprandial  decrease dose by 25% q 6-8 weeks until the   •  Gastrointestinal  side  effects  are  possible
            ○   Infectious disease testing (tick-transmitted/   lowest effective dose is achieved. Complete   with  all  treatments:  famotidine  1 mg/kg
              protozoal/fungal infection)       withdrawal is possible in some cases.  PO  q  24h  or  omeprazole  1 mg/kg  PO  q
                                                                2
                                              •  Cytarabine  200  mg/m  IV constant-rate   24h might help prevent gastric ulceration.
           Advanced or Confirmatory Testing     infusion (CRI) over 8 hours (25 mg/m /h   Excessive vomiting, especially with blood, or
                                                                            2
                                                                        2
           •  MRI of brain (p. 1132): focal to multifocal   ×  8  hours  [p.  609])  or  50  mg/m   SQ  q   anorexia necessitates a medication change.
            T2- and FLAIR-weighted hyperintensities   12h  for  4  doses.  Repeat  q  3  weeks  for  4   ○   Administer cyclosporine on an empty
            throughout cerebral cortex; occasional   cycles, increasing the treatment interval by   stomach; if excessive vomiting, freeze the
            involvement of cerebellum and brainstem   1 week q 4 cycles until q 8 week treatment   capsule and/or administer metoclopramide
            variable contrast enhancement       schedule is reached. Recent studies suggest   or maropitant 30 minutes before dosing.
           •  CSF analysis (pp. 1080 and 1323): elevated   a longer survival time with CRI than SQ   •  Myelosuppression: perform complete blood
            nucleated cell count and total protein  administration.                counts to monitor
           •  Cytology: > 50% mononuclear, varied lower   •  Cyclosporine  (Atopica)  5-10  mg/kg  PO     ○   Cytarabine: 1 week after administration
            percentages of nondegenerative neutrophils  q 12h                        and before each treatment
           •  Paired  distemper  titers  (serum  ±  CSF):   ○   To reduce cost, can be administered q 24h   ○   Procarbazine:  every  week  for  the  first
            normal                                with ketoconazole 8 mg/kg PO q 24h  month, then monthly

                                                     www.ExpertConsult.com
   1281   1282   1283   1284   1285   1286   1287   1288   1289   1290   1291