What Is Your Neurologic Diagnosis? - AVMA Journals

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What Is Your Neurologic Diagnosis? A

n 11-month-old 3.66-kg (8.05-lb) castrated male domestic shorthair cat was evaluated because of a history of hypnic jerks since the owners acquired him. The cat had been found roadside at 2 weeks of age and had since been an indoor cat in a multicat household. Hypnic jerks are brief, myoclonic muscle twitches that occur at sleep onset occasionally in clinically normal individuals. This cat’s hypnic jerks had progressed to focal seizures with impaired consciousness 4 months

prior to evaluation. The seizures involved sudden bursts of violent activity and altered consciousness. Initially, seizures occurred several weeks apart but increased in frequency with multiple seizures occurring 2 weeks prior to evaluation. Treatment with diazepam (0.5 mg, PO, administered in the evenings) was initiated for 1 week prior to evaluation; however, the seizures continued to increase in frequency and severity. Physical examination findings were considered normal.

Neurologic examination Observation Mental Posture Gait Paresis Other

Alert X Normal X Normal Pelvic limbs

Depressed Head tilt Ataxia X Tetra

Disoriented Tremor Pelvic limbs Hemi

Stupor Falling All 4 Mono

Coma Circling

Key: 4=exaggerated, clonus; 3=exaggerated; 2=normal; 1=diminished; 0=none; NE=not evaluated

Postural reactions Wheelbarrow Hopping Ext postural thrust Proprioceptive pos Hemistand/walk Placing–tactile Placing–visual

Spinal reflexes Quadriceps Extensor carpi Flexion Crossed extensor Perineal

LF

RF

NE 2

NE 2

2 NE 1 NE

2 NE 2 NE

LF

RF

NE 2 0

Cranial nerves

II, VII–Vision menace II, III–Pupils resting Stim L Stim R II–Fundus III, IV, VI–Strabismus, resting III, IV, VI, VIII–Strabismus, position

LR

RR

2 2 2 NE

2 2 2 NE

LR

RR

2

2

2 0 2

2 0 2

NE 2 0 L

R

0 2 2 2 2 0 0

2 2 2 2 2 0 0

VIII–Nystagmus, resting VIII–Nystagmus, change V–Sensation VII–Facial mm V, VII–Palpebral flex IX, X–Gag XII–Tongue

L

R

0 0 2 2 2 2 2

0 0 2 2 2 2 2

Comments CN

Physiologic nystagmus was present bilaterally.

Sensation (Locate and describe abnormal) Hyperesthesia Superficial pain Cutaneous reflex Deep pain

0 2 2 NE

What is the problem? Where is the lesion? What are the most probable causes of this problem? What is your plan to establish a diagnosis? Please turn the page. JAVMA, Vol 242, No. 12, June 15, 2013

Vet Med Today: What Is Your Neurologic Diagnosis?

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Assessment Anatomic diagnosis Rule out location

Problem Absent menace response in the left eye and lateralized visual field deficits with intact facial and pupillary light reflexes

Right cerebrum or thalamus (visual cortex or lateral geniculate nucleus) or left cerebellum

Left thoracic limb overreaching and loss of endpoint control

Right cerebrum or subcortical nuclei (motor cortex, corticospinal tracts, or basal nuclei) or left cerebellum

Seizures

Cerebral cortex

Likely location of one lesion These signs are best explained by neurolocalization to the right cerebrum.

Etiologic diagnosis—Rule out disease processes included anomalous or developmental disorders, inflammatory and infectious diseases (toxoplasmosis, cryptococcosis, blastomycosis, histoplasmosis, feline infectious peritonitis, FeLV or FIV infection, and parasitic infestation [eg, cuterebriasis]). The diagnostic plan included a CBC, serum biochemical analysis, assessment of serum thyroxine concentration, urinalysis, and serologic testing (to rule out underlying systemic diseases) and MRI of the brain (to evaluate for structural lesions). Because of the asymmetric signs on neurologic examination, a structural lesion was considered more likely than metabolic or toxin encephalopathies, which were more likely to be associated with symmetric deficits. Diagnostic test findings—Results of serologic testing indicated that the cat was negative for antibodies against Toxoplasma gondii, FIP virus, and FIV and antigen from Cryptococcus spp and FeLV. Results of the serum biochemical analysis were unremarkable, and serum free thyroxine concentration was within reference range. Multiplanar 3-mm T2-weighted (T2W), fluid-attenuated inversion recovery (FLAIR), T1-weighted (T1W) images (obtained prior to administration of contrast medium), and gradient echo T2*-weighted sequences (T2*W) were obtained. Following IV administration of gadodiamidea (0.2 mL/kg [0.09 mL/lb]), multiplanar T1W images were obtained. Magnetic resonance imaging revealed that the right lateral ventricle was dilated and abnormally shaped; a subdural free water signal was present (Figure 1). All fluid signals present in T2W images were suppressed in FLAIR images; this finding was consistent with a low-protein, low-cellularity fluid. The cerebral cortex adjacent to the cavity was markedly thinned with a lack of distinct gyri and sulci. In T2*W sequences, a signal void was evident in the dependent region of the right ventricle of the diencephalon; the signal void was surrounded by a hyperintense ring at the level of the third ventricle. When colocalized with other sequences, the signal void present in the T2*W images was hypointense in T1W images and isointense in T2W images, most consistent with chronic hemorrhage. Following contrast medium administration, minimal contrast enhancement was visible at the edge of the right frontal sinus on T1W 1642


Figure 1—Transverse T2-weighted image of the head of an 11-month-old cat that was evaluated because of a history of hypnic jerks that had progressed to focal seizures with impaired consciousness 4 months prior to evaluation; the seizures were continuing to increase in frequency and severity. Communication between the right lateral ventricle, a porencephalic cyst, and the subarachnoid space is evident. The remainder of the ventricular system appears normal in size.

images. On the basis of MRI findings, other neoplastic, infectious, inflammatory, or metabolic diseases were determined to be unlikely. Analysis of a CSF sample was not performed because the cat was awakened from anesthesia before contrast enhancement was identified via MRI. Comments Abnormalities detected during neurologic examination are sensitive and specific predictors of the presence of abnormalities detectable via MRI in dogs with seizures.1 In most cats with epilepsy, an underlying cause of seizures can be identified; thus, advanced diagnostic testing should be encouraged for cats with epilepsy, particularly if abnormalities are evident during neurologic examination.2–5 For the cat of this report, MRI revealed a CSF-filled cavity within the brain that communicated with the right lateral ventricular system and subarachnoid space (ie, porencephaly).6,7 A porencephalic cyst develops when an insult to the brain parenchyma occurs after neuronal migration but prior to glial cell differentiation JAVMA, Vol 242, No. 12, June 15, 2013

and activation. As a result, there is an insignificant astrocyte reaction and little or no perilesional gliosis.8,9 In humans, porencephaly develops most commonly because of vascular insults during the fetal period, which result in failure of cerebral perfusion and loss of normally developed cortical tissue.10 In addition to porencephaly caused by such parenchymal insult (type I or encephaloclastic or destructive porencephaly), porencephaly can be the result of a developmental anomaly (type II porencephaly). Type II porencephaly can be associated with a spectrum of lesions.11 In veterinary medicine, porencephaly is generally encephaloclastic because of destructive processes such as periventricular hemorrhage or a CNS infection. To date, no infectious agent has been identified in the etiopathogenesis of porencephaly, and genetic defects leading to neuronal migration disorders (type II porencephalies) are rare in cats; however, both griseofulvin and panleukopenia have been implicated in brain malformations in dogs and cats.12,13 A left-sided menace response and visual deficits with intact reflexes correspond with right cerebral localization. Dysmetria is most commonly associated with cerebellar lesions or damage to the spinocerebellar tracts in the cervical spinal cord. Animals with telencephalon lesions, however, will also have a dysmetric gait attributable to destruction of portions of the extrapyramidal system, specifically the basal nuclei.14 The causal relationship between porencephaly and seizures has not been established; however, some of the proposed mechanisms include cystic hypertension, cortical dysplasia resulting in the formation of a seizure focus, and hippocampal sclerosis secondary either to seizures or altered communication between the hippocampus and areas of abnormal cortical tissue.12,15 Epileptic children experience repetitive hypnic jerk events, which may be related to an intensification of an otherwise normal event owing to the lack of strong inhibitory influence resulting from intracranial lesions.16 Because of the potential contrast enhancement of the right frontal sinus in the cat of the present report, cefadroxil (22 mg/kg [10 mg/lb], PO, q 12 h) was prescribed, but the cat had emesis. The owner was advised to discontinue the antimicrobial treatment and monitor for progression of clinical signs. The cat was treated with levetiracetam (100 mg/mL oral solution; 20 mg/kg [9.1 mg/lb], PO, q 8 h)17; at 7 months after starting that treatment, the frequency and severity of seizure activity had decreased. No treatment of the porencephalic cyst was required. Prognosis for cats with porencephaly is unknown; however, in affected cats with seizures, prognosis should be good with medical treatment and control of seizures. a.

Omniscan, GE Healthcare Inc, Princeton, NJ.

References 1.

2. 3. 4. 5.

6. 7.

8. 9. 10. 11. 12. 13. 14. 15. 16.

17.

Bush WW, Barr CS, Darrin EW, et al. Results of cerebrospinal fluid analysis, neurologic examination findings, and age at the onset of seizures as predictors for results of magnetic resonance imaging of the brain in dogs examined because of seizures: 115 cases (1992–2000). J Am Vet Med Assoc 2002;220:781–784. Barnes HL, Chrisman CL, Mariani CL, et al. Clinical signs, underlying cause, and outcome in cats with seizures: 17 cases (1997–2002). J Am Vet Med Assoc 2004;225:1723–1726. Pakozdy A, Leschnik M, Sarchahi AA, et al. Clinical comparison of primary versus secondary epilepsy in 125 cats. J Feline Med Surg 2010;12:910–916. Quesnel AD, Parent JM, McDonell W, et al. Diagnostic evaluation of cats with seizure disorders: 30 cases (1991–1993). J Am Vet Med Assoc 1997;210:65–71. Schriefl S, Steinberg TA, Matiasek K, et al. Etiologic classification of seizures, signalment, clinical signs, and outcome in cats with seizure disorders: 91 cases (2000–2004). J Am Vet Med Assoc 2008;233:1591–1597. MacKillop E. Magnetic resonance imaging of intracranial malformations associated with dogs and cats. Vet Radiol Ultrasound 2011;52:S42–S51. de Lahunta A, Glass EN. Cerebrospinal fluid and hydrocephalus. In: De Lahunta A, Glass EN, eds. Veterinary neuroanatomy and clinical neurology. 3rd ed. St Louis: Saunders Elsevier, 2009; 54–76. Low C, Garzon E, Carrete H Jr, et al. Early destructive lesions in the developing brain: clinical and electrographic correlates. Arq Neuropsiquiatr 2007;65:416–422. Raybaud C. Destructive lesions of the brain. Neuroradiology. 1983;25:265–291 Haberland C. Fetal and perinatal cerebral pathology. In: Clinical neuropathology: text and color atlas. New York: Demos Medical Publishing, 2007;299–307. Mancini GMS, de Coo IFM, Lequin MH, et al. Hereditary porencephaly: clinical and MRI findings in two Dutch families. Eur J Paediatr Neurol 2004;8:45–54. Davies ES, Volk HA, Behr S, et al. Porencephaly and hydranencephaly in six dogs. Vet Rec 2012;170:179. Schmidt MJ, Klump S, Amort K, et al. Porencephaly in dogs and cats: magnetic resonance imaging findings and clinical signs. Vet Radiol Ultrasound 2012;53:142–149. de Lahunta A, Glass E. Upper motor neuron. In: De Lahunta A, Glass E, eds. Veterinary neuroanatomy and clinical neurology. 3rd ed. St Louis: Saunders Elsevier, 2009;192–220. Ho SS, Kuzniecky RI, Gilliam F, et al. Congenital porencephaly: MR features and relationship to hippocampal sclerosis. AJNR Am J Neuroradiol 1998;19:135–141. Fusco L, Pachatz C, Cusmai R, et al. Repetitive sleep starts in neurologically impaired children: an unusual non-epileptic manifestation in otherwise epileptic subjects. Epileptic Disord 1999;1:63–67. Bailey KS, Dewey CW, Boothe DM, et al. Levetiracetam as an adjunct to phenobarbital treatment in cats with suspected idiopathic epilepsy. J Am Vet Med Assoc 2008;232:867–872.

This report was submitted by Baye G. Williamson, DVM, and Dennis P. O’Brien, DVM, PhD, DACVIM; from the Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211. Address correspondence to Dr. Williamson (williamsonbg@missouri. edu).

This feature is published in coordination with the American College of Veterinary Internal Medicine on behalf of the specialty of neurology. Contributors to this feature should contact Dr. Helen L. Simons (800-248-2862, ext 6692) for case submission forms. Submissions will be sent to Dr. Karen Kline, DVM, DACVIM, for her review, except when Dr. Kline is an author.

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