NOTE

Hydrocephalus and Syringomyelia in a Cat

Kenji TANI1), Atsuo TAGA1), Kazuhito ITAMOTO1), Takeshi IWANAGA2), Satoshi UNE1), Munekazu NAKAICHI1) and Yasuho TAURA1)*

1)Department of Veterinary Surgery, Faculty of Agriculture, Yamaguchi University, Yoshida 1677–1, Yamaguchi 753–8515 and 2)Hayashiya Animal Hospital Momo, Momoyama-cho Yamanoshita 32, Fushimi-ku, Kyoto 612–8002, Japan

(Received 12 March 2001/Accepted 6 August 2001)

ABSTRACT. A 3-month-old male Japanese cat with feline parvovirus infection, showing central and cervical nerve abnormalities, was diag- nosed as and syringomyelia by use of magnetic resonance imaging (MRI). The cat was maintained clinically by medical treatment even though he could not stand. The MRI scans obtained about 5 months later showed that the ventricles had increased in size and the cervical syrinx had extended into the thoracic . Ventriculoperitoneal (VP) shunt was performed. One week after surgery, neurological conditions had improved. At the postoperative MR images, the ventricles had decreased in size and the syrinx in the cervical and thoracic spinal cord could no longer be seen. The cat was still alive and was able to walk well. KEY WORDS: feline, magnetic resonance imaging, syringomyelia. J. Vet. Med. Sci. 63(12): 1331–1334, 2001

Hydrocephalus is a term commonly used to describe a the palpebral reflex were normal. Asymmetry of the pupils condition involving abnormal dilatation of the ventricular was also observed. Patellar reflexes were exaggerated and system within the cranium [11, 15]. Viral infections such as flexor reflexes were detected in all four limbs. Elevated rec- feline infectious peritonitis (FIP) are a common cause of tal temperatures (40.8, 40.6 and 39.6°C) were noted on days hydrocephalus in cats [15, 18]. Syringomyelia has been 7, 8 and 9, respectively. Leukocytopenia (3,400, 1,100 and defined as fluid-filled cavities in the substance of the spinal 1,900/µl) was noted on days 11, 12 and 13, even though no cord, with destruction of the nervous tissue [19]. Its cause is gastrointestinal signs were present. The stools were positive unknown, but it may be associated with or result from for Parvovirus antigen on day 11. Serum titers of immuno- hydrocephalus [16, 24]. Ventriculoperitoneal (VP) shunts globulin (Ig) M and IgG antibodies against Parvovirus anti- are commonly used to divert the flow of gens were 640 and less than 10 times the levels in the (CSF) from the ventricles of the brain to the peritoneal cav- negative controls, respectively. Serum samples were nega- ity in human [11], and have proved to be an tive for FIP. effective surgical treatment for hydrocephalus in dogs [15] Survey radiographs of the skull and cervical vertebrae, and cats [23]. Several investigators [12, 15, 16, 24] in the taken with the in both neutral and flexed positions, veterinary field have suggested magnetic resonance imaging showed no unusual features. Ultrasonography through the (MRI) to be a useful technique for the antemortem diagnosis fontanelles showed marked dilatation of the lateral and third of several cranial and spinal disorders in animals. This arti- ventricles. In addition, MRI examinations were performed cle describes the clinical findings in, and management of, a on days 37, 182, 216 and 308, using a 0.2-Tesla system cat with hydrocephalus and syringomyelia, together with (HITACHI MRP20) with a QD coil designed for scanning temporal changes in MR images obtained before and after the human knee joint. The slice thickness was 2.5 mm and the insertion of a VP shunt. the field of view was 200 mm. Taking into consideration the A 3-month-old male Japanese cat was referred because of cat’s condition, T1-weighted sagittal and dorsal imaging of severe ataxia following an inadvertent fall onto the floor the cervical spinal cord was undertaken, and complete imag- from a height of about 2 m. The cat had not been vaccinated ing of the head was performed without sedation during the against any diseases. The owner stated that the cat had first MRI. Marked dilatation of the lateral, third and fourth walked well until the event. Laboratory examination ventricles, and of the aqueduct of the cerebrum, was recog- revealed neutrophilia (56,400/µl; Segmented neutrophils nized as hypointense areas in the T1-weighted images and 99%, Lymphocytes 1%). Physical examination revealed as hyperintense areas in the T2-weighted images. A syrinx severe muscular atrophy over the whole body and myotonus was detected as a hypointense area in the spinal cord of all four limbs. Neurological examination revealed sev- between the C2 and C3 cervical vertebrae in the T1- eral cranial nerve abnormalities such as torticollis to the weighted images (Fig. 1a). An additional longitudinal area right, nystagmus and depression, and cervical nerve abnor- of hypointensity between C1 and C5 in the T1-weighted malities such as clasp-knife rigidity of fore limbs. The men- images was considered to be the spinal canal. At this point, ace response was absent, but the papillary light reflex and hydrocephalus and syringomyelia were diagnosed, and oral furosemide (1 mg/kg twice daily) was administered at the *CORRESPONDENCE TO: TAURA, Y., Department of Veterinary Sur- gery, Faculty of Agriculture, Yamaguchi University, Yoshida owner’s request. The cat was maintained clinically, even 1677–1, Yamaguchi 753–8515, Japan. though he could not stand without help. 1332 K. TANI ET AL.

Fig. 1. (a, b, c). Sagittal T1-weighted MRI scans of the syringomyelic cavity in the cervical spinal cord. TR=500 ms, TE=25 ms. (a): The syrinx (arrow) was detected as a hypointense area in the cervical spinal cord (C2 -3). (b): The first postoperative scan shows that the syrinx (arrow) had extended throughout the cervical spinal cord. (c): The syrinx had disappeared 105 days after surgery.

The second MRI scan showed that the ventricles had increased in size since the first MRI scan. Cervical scanning was not performed on this occasion. Because the disease appeared to be progressing, the furosemide dose was increased to 1.5 mg/kg twice daily and oral predonisolone (0.5 mg/kg daily) was added. As hypokalemia (3.0–3.5 mEq/L) was noted during this treatment, oral potassium chloride (0.02 g/kg twice daily) was administered. The decision to perform surgery on the cat was made on day 205. We used Ficon shunt systems (Fuji Systems Cor- poration, Japan) and a low-pressure valve was chosen. The Fig. 2. (a, b). Transverse T1-weighted MRI scans of the syrin- gomyelic cavity in the cervical spinal cord. TR=500 ms, ventricular catheter was placed into the left lateral ventricle TE=25 ms. (a): The syrinx (arrow) was detected as a through the parietal bone. The CSF pressure was not mea- hypointense area in the cervical spinal cord (C2). (b): The syr- sured because the spontaneous CSF flow was greater than inx in the cervical spinal cord (C2) disappeared 105 days after expected during the operation. The distal end of the catheter surgery. Parenchyma of the spinal cord were recognized in was implanted into the peritoneal cavity. Subcutaneous pre- spite of the syringomyelic cavity, although hyperintense donisolone (1 mg/kg) was administered initially, then grad- lesions in the vertebral canal (arrow head) were also recog- ually tapered off over the course of a week. CSF collected nized. through the catheter during surgery was clear and colorless, with a refractive index of 1.007, a total nucleated cell count connection between the syrinx in the spinal cord and the of 0.5 cells/ml and a protein concentration of 12 mg/dl. fourth ventricle. One week after surgery, the nystagmus, These results were considered normal. depression and neurological conditions had improved. For the third and fourth MRI scans, the cat was sedated Some invasive care was needed during the 3 months after with intravenous (iv) diazepam (0.5 mg/kg) and butorphanol surgery because the distal catheter became kinked several tartrate (0.05 mg/kg, iv). He was then anesthetized with times. The cat was able to walk well, even though he still isoflurane. At the third (first postoperative) MRI, a subdural had mild torticollis and asymmetry of the pupils on day 410. hematoma was detected as an area of hyperintensity in both Syringomyelia has rarely been reported in cats [1, 6, 20, the T1- and T2-weighted images of the left cerebral hemi- 25], although it is well known that experimental syringomy- sphere. Another lesion, which showed as a hypointense area elia can be induced by kaolin in cats [8–10], rabbits [3] and in the T1-weighted images and as a hyperintense area in the dogs [4]. According to Milhorat et al. [22], syringomyelia T2-weighted images, was recognized in the subdural space can be classified into three types: (1) dilatations of the cen- (mainly over the right cerebral hemisphere), and was tral canal that communicate directly with the fourth ventri- assumed to be a collection of CSF together with blood and/ cles, also known as hydromyelia; (2) non-communicating or inflammatory substances. Some collapse of the brain was dilatations of the that arise below a syrinx-free also observed. The syrinx was found to have extended into segment of the spinal cord; and (3) extracanalicular syrinxes the cervical (Figs. 1b and 2a) and thoracic spinal cord. that originate within the parenchyma of the spinal cord and At the fourth MRI on day 308, the ventricles had do not communicate with the central canal. The clinical decreased in size and the syrinx in the cervical (Figs. 1c and course of the cat described in the present report suggests that 2b) and thoracic spinal cord could no longer be seen, the most likely diagnoses were hydrosyringomyelia or although the MR images still differ from those in normal hydromyelia. However, no connection between the syrinx dog. The clinical course did not confirm the presence of a in the spinal cord and the fourth ventricles was detected on HYDROCEPHALUS AND SYRINGOMYELIA IN A CAT 1333 the MR images, and no histopathological examination has by ventriculography, but did not mention what occurred in been performed because the cat is still alive at the time of the brain after surgery. Other reports have indicated that writing; thus, the authors diagnosed the cat as having syrin- reconstitution of the cerebrum after shunting occurs only in gomyelia on the basis of the MRI results. the [5, 7, 14, 21, 26, 27]. In our case, the ven- The pathogenesis of the hydrocephalus and syringomye- tricles did not differ significantly in size at the first and forth lia in the present case is unclear. Interestingly, the cat was MRI scans, but the syrinx was no longer recognizable at the positive for parvovirus antigen but negative for FIP anti- fourth MRI. Harrington et al. [15] suggested that hydro- body. Tamke et al. [25] reported acquired hydrocephalus cephalus should be aggressively treated as early as possible, and hydromyelia in a cat with FIP. In addition, in utero because neuronal loss and laminar cortical destruction are infection with Parvovirus can cause cerebellar hypoplasia, irreversible. If shunt placement was performed on an early which affects the external germinal layer of the stage of hydrocephalus in this cat, significant reconstitution and prevents the formation of the granular layer. Both of the cerebrum and cerebellum might have been achieved, and hydrocephalus have been known to as suggested by the MR images. Communicating syringo- occur concurrently with parvovirus infection [13, 15]. On myelia has been managed surgically in humans [8, 17], the other hand, experimentally induced hydrocephalus while VP shunting [2] and laminectomy [16] have been used becomes apparent within 1 to 2 weeks of a kaolin injection in dogs. Although the ideal surgical management for cats [5, 7, 9, 10, 14, 21, 26, 27] and the central canal dilates with syringomyelia remains unknown, VP shunting was an within 2 to 6 weeks [9, 10]. As regards parvovirus infection, effective treatment for communicating syringomyelia asso- serum IgM and IgG levels have indicated that the infection ciated with hydrocephalus in the present animal. There has is established within 3 days to 3 weeks after contact (Unpub- been no evidence of shunt complications in this cat after a lished information; Nikken Bio Medical Laboratory Inc., postoperative follow-up period of 360 days. Japan). These observations suggest that the hydrocephalus and syringomyelia seen in the present subject might have ACKNOWLEDGEMENTS. The authors would like to been associated with the acquired feline parvovirus infec- thank Dr. Sonoda for referring this case and Dr. Chusnul for tion. his critical suggestions during the preparation of the manu- Ultrasonography is useful for brain imaging in animals script. because it can usually be performed while they are awake. However, in this case, MRI supplied more detailed informa- REFERENCES tion than ultrasonography throughout the clinical course, especially after the cat’s skull had become completely ossi- 1. Bone, D. L. and Wilson, R. B. 1982. J. Am. Vet. Med. Assoc. fied. Taga et al. 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