Segmental hypoplasia of the spinal cord and syringomyelia in a calf

ABSTRACT: Congenital malformations are functional and structural changes in organ systems, tissues, or organs that may develop during the embryonic or fetal phase. Spinal cord malformations, such as segmental hypoplasia of the spinal cord (SHSC) and syringomyelia, are rare in bovines. A Girolando calf from Valença, Rio de Janeiro, was admitted to the Veterinary Hospital of Universidade Federal Rural do Rio de Janeiro because of motor incoordination. Clinical evaluation revealed a 5-cm depression area in the spine at the dorsal line of the thoracic region. Neurological examination revealed reduced proprioception, pelvic limb extension with increased nociceptive activity, and reduced anal reflex. In radiographic examination, the body of the T11 vertebra had a trapezoidal wedge shape with ventral hemivertebra, probable agenesis or hypoplasia of the T11-T12 spinous processes, and fusion of the T9-T10 spinous processes. Myelography revealed extradural spinal compression caused by vertebral malformations. Necropsy showed no spinous processes (T11-T12), cranial stenosis in the medullary canal (T11-T13), and 1-3-mm pores in the white matter of the thoracic spinal cord (T8-T11). Microscopy revealed cystic dilatations in the white matter (T9-T11), cystic areas of varying sizes (T8-T9), and moderate reduction in the gray matter around the central canal of the medulla (T11-T13). Here, we reported the clinical and pathological findings of SHSC and syringomyelia in a Girolando calf. The features should be differentiated from other spinal cord syndromes. Congenital malformations are of economic importance, and their etiology and diagnosis are fundamental to disease control and progenitor-selection programs.


Souza et al.
Congenital malformations are functional and structural changes in organ systems, tissues, or organs that may occur in the embryonic or fetal phase (DANTAS et al., 2010;MACEDO et al., 2011). Their etiology in cattle may be associated with infectious agents, ingestion of toxic plants, chemical agents, nutritional deficiencies, and hereditary factors (DE LAHUNTA & GLASS, 2009;CANTILE & YOUSSEF, 2016).
Segmental hypoplasia of the spinal cord (SHSC) develops during embryogenesis and is characterized by incomplete formation of one or more segments of the spinal cord, mainly in the thoracolumbar region (CANTILE & YOUSSEF, 2016). Hypoplasia at T3-L3 causes functional disability of the pelvic limbs (DE LAHUNTA & GLASS, 2009). It is a rare malformation and is reported particularly in cattle breeds, such as Angus, Hereford, Simmental, Charolais, and Shorthorn (DOIGE et al., 1990). The SHSC has been reported in the Holstein (BINANTI et al., 2012;YILDIRIM et al., 2013), Angus (LEIPOLD et al., 1993), and Japanese Black (IMAI & MORITOMO, 2009)

breeds.
Syringomyelia is the formation of tubular cavitations in the spinal cord not surrounded by the ependyma and separated from the central canal, which distinguishes this medical condition from hydromyelia. Possible causes of the development of congenital syringomyelia are the presence of anomalous vascular pattern and ischemia, which can lead to infarction and a series of events that alter the cerebrospinal fluid (CSF) flow dynamics (CANTILE & YOUSSEF, 2016).
The diagnoses of SHSC and syringomyelia are based on the clinical and epidemiological histories and findings of imaging, necropsy, and histopathology (BRAUND, 1993). Here in, we reported the clinical and pathological findings of SHSC and syringomyelia in a Girolando calf.
A 15-day-old calf from Valença, Rio de Janeiro, born from a natural mount of a purebred Holstein bull and a multiparous half-blood Girolando cow, was admitted to the Veterinary Hospital of the Universidade Federal Rural do Rio de Janeiro (UFRRJ) because of motor incoordination. The clinical history was obtained from the responsible veterinarian. After the ingestion of colostrum, the calf had been separated from its progenitor, and a depression in the lower back had developed. A few days later, ataxia was observed, and from day 7, the calf permanently remained in the supine position and underwent artificial milk-feeding. After an infectious etiology was suspected, a blood sample of the progenitor was sent to the Virology Laboratory of the Universidade Federal do Rio Grande do Sul (UFRGS) to search for the bovine viral diarrhea virus (BVDV) RNA through reverse transcription polymerase chain reaction (RT-PCR).
During the clinical evaluation, the calf remained in the supine position and could not stand even with assistance. It had active behavior, body weight of 46 kg, normal-colored ocular and oral mucosae, capillary refill time of 2 s, normal skin turgor, suction reflex, heart rate of 156 beats/ minute, respiratory rate of 88 breaths/minute, and rectal temperature of 39.9 °C. In the spine, there was an area with a 5-cm depression at the dorsal line of the thoracic region (T11 and T12). Neurological examination revealed pelvic limb extension, reduced proprioception, increased nociceptive activity in the pelvic limbs, and reduced anal reflex.
The calf was referred to the UFRRJ Diagnostic Imaging Sector for radiography and myelography. Sedation was performed with propofol 5 mg/kg for induction and 0.5 mg/kg/min for maintenance. Radiography revealed that the body of the T11 vertebra had a trapezoidal wedge shape, probably due to ventral hypoplasia, with ventral hemivertebra. Moreover, there were probable agenesis or hypoplasia of the spinous processes of T11 and T12 and fusion of the spinous processes of T9 and T10 ( Figure 1A).
For myelography, a non-ionic contrast (Iohexol 300 mg/mL) was administered via the brain-medullary cistern at 0.5 mL/kg. Contrastcolumn narrowing was observed with deviation toward the spinal cord from the T10-T12 caudal region, indicating extradural spinal cord compression caused by vertebral malformations, particularly of T11 ( Figures 1B and 1C). Due to the unfavorable prognosis, the calf was euthanized, and necropsy was performed by the team of the Pathological Anatomy Sector of UFRRJ. Fresh fragments from the central nervous system, lungs, thymus, and spleen were collected to search for the BVDV RNA through RT-PCR. The remaining organs were fixed in 10% buffered formalin and routinely processed for histopathology.
During necropsy, the external examination revealed a dorsal line depression of T11 (Figures  2A and 2C). In the internal evaluation, the spinous processes of the T11-T12 vertebrae were not observed. The medullary canal showed cranial stenosis at the level of T11-T13 ( Figures 2B and 2C). In the T10 and T11 vertebrae, the ventral surface of the medullary body had a concavity headed to the dorsal region ( Figure 2C). At the cross-section of the thoracic spinal cord (T8-T11), 1-3-mm cystic areas were reported in the white matter, characteristic of syringomyelia, corresponding to the hypoplastic area ( Figure 2D).
On microscopy, the T9-T11 segments showed bilateral and ventral cystic dilatations in the white matter (accentuated syringomyelia). The syringomyelia of segments T8 and T9 presented with distinct conformation, characterized by the formation of cystic areas of varying sizes ( Figure 2E). In the T9 segment, large cystic areas were observed in the ventral and dorsal spine regions, and small cysts were observed around the vessels, which generated deformation of the medullary gray matter. The T11-T13 segments showed a moderate reduction in the gray matter around the central canal of the spinal cord (hypoplasia). In the remaining gray matter of the medullary segments of the atlas, pericariae of neurons with dissolution of the Nissl substance and nuclear pyknosis (chromatolysis) were observed from the T8-T9, T13, and L2-L3 cervical intumescence. The medullary T10 segment and obex presented with central medullary canal ectasia (hydromyelia).
The RT-PCR was performed on samples of the progenitor's blood serum and calf's organs for fragment detection of 119 base pairs of 5'UTR region pestivirus, and the results were negative.
In Brazil, the main causes of congenital malformations in ruminants are the ingestion of toxic plants, such as Mimosa tenuiflora (PIMENTEL et al., 2007;DANTAS et al., 2010) and Poincianella pyramidalis (REIS et al., 2016;MARCELINO et al., 2017), restricted to the Caatinga Biome, in the semiarid region of Northeast Brazil, and absent from the property in the present report. Other infectious agents of congenital malformations and reproductive alterations, such as embryonic death and abortion, In the dairy basin from which this calf originated, a molecular diagnosis of BVDV infection had been performed in a cow that aborted a 4-monthold fetus (LOPES et al., 2016). Pestiviruses have teratogenic potential in ruminants (PAVARINI et al., 2008;OTTER et al., 2009;DEZEN et al., 2013). The samples in this report were negative for BVDV in PCR, which does not rule it out as a possible etiological agent of malformations, since BVDV-infected fetuses are immunocompetent after 125 days of gestation, thus eradicating the virus (RIDPATH et al., 2012).
Spinal cord injuries caused by BVDV are relatively rare in bovine fetuses compared to infected sheep fetuses (OTTER et al., 2009). Intrauterine BVDV infection causes mainly cerebellar dysplasia and may be associated with hydranencephaly, hydrocephalus, microcephaly, or porencephaly (VELDHUIS et al., 2013).
Other causes associated with malformations are radiation, cortisones, benzimidazoles, sulfonamides, and organophosphorus compounds. (LEIPOLD & DENNIS, 1986). In the present report, during the epidemiological evaluation, the clinical history did not lead to the suspicion of teratogenic agents.
As in the present report, YILDIRIM et al. (2013)  nervous system of a calf with SHSC, suggesting that this lesion may be associated with an anomaly of organogenesis and dependent on a genetic aberration. Congenital defects are reported worldwide, mainly in the Holstein breed. They can be a typical breed change as the cattle have shared ancestors owing to intensive genetic improvement (AGERHOLM et al., 2001). Thus, the Girolando calf in this report could carry a mutant allele that led to the congenital defect. Similarly, BURGSTALLER et al. (2015) did not rule out the hypothesis of a congenital disorder in a newborn calf with syringomyelia.

detected no inflammatory infiltrates in the
Myelodysplastic syndromes, including brachyspine syndrome, Perosomus elumbis infection, and complex vertebral malformation, are reported more frequently than SHSC in calves and should be differentiated from other congenital spinal cord syndromes. The brachyspine differs from SHSC by the presence of a short neck, short trunk, smaller vertebrae, normal limbs, mandibular hypoplasia, and misaligned teeth (TESTONI et al., 2012). Perosomus elumbis is characterized by agenesis or aplasia of the lumbar, sacral, and coccygeal vertebrae, which causes shortening of the animal's body, arthrogryposis of the pelvic limbs, malformation of the musculature, and spinal cord dysplasia (LOPES et al., 2016). In complex vertebral malformations, there are skeletal deformities, deformed vertebrae, hemivertebrae, ankylosis, mainly cervicothoracic, scoliosis, and symmetrical arthrogryposis of the lower limbs (WHITLOCK et al., 2008). Spina bifida is the absence of the dorsal portion of the vertebrae and is usually accompanied by various forms of myelodysplasias (BORGES et al., 1997).
The morphological findings and clinical signs are consistent with SHSC and similar to other cases described in bovines (IMAI & MORITOMO, 2009;BINANTI et al., 2012;TESTONI et al., 2012;YILDIRIM et al., 2013;BURGSTALLER et al., 2015). In the histopathological analysis of the spinal cord, as seen by ALBERNAZ et al. (2014), depletion of the dorsal and ventral gray horns and reduced white matter structures were observed, confirming SHSC. TESTONI et al. (2012) reported muscle stiffness and atrophy of the pelvic limbs, which differs from the findings reported in this calf. YILDIRIM et al. (2013) reported syringomyelia in a calf with SHSC with no vertebral abnormalities, unlike the calf in the present report. BURGSTALLER et al. (2015) reported syringomyelia in a Simmental calf with clinical and morphological signs similar to the calf in this report.
SHSC is associated with a combination of hydromyelia, syringomyelia, absence or interruption of the central canal, and gray matter dysplasia (SUMMERS et al., 1995;CANTILE & YOUSSEF, 2016). In the present report, the calf had hydromyelia, syringomyelia, gray matter hypoplasia (gray horns), and neuronal necrosis. A series of events, such as senility, trauma, infection, or neoplasia, that alter the CSF flow dynamics can lead to fluid accumulation, increased pressure, and spinal cord cavitation called syringomyelia (CANTILE & YOUSSEF, 2016). Lesions observed on macroscopy and microscopy were sufficient to explain the neurological and medical condition of the spinal cord of this calf. Alterations in the vertebral body and spinous process probably altered the bone dynamics and headed the vertebral body dorsally, which caused spinal cord stenosis and consequent syringomyelia. In humans, SHSC usually causes constriction of the spinal canal and focal vertebral anomalies, and they are associated with spinal dysplasia (YILDIRIM et al., 2013).
SHSC and syringomyelia are rare malformations in calves and should be distinguished from other congenital spinal cord syndromes. Congenital malformations are of economic importance, and their etiology and diagnosis are fundamental for disease control and progenitor-selection programs. For the calf in the present report, radiography and myelography contributed to the diagnosis, indicating bone malformations and spinal cord compression. However, SHSC and syringomyelia could be diagnosed only through necropsy and histopathology. Souza et al. collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.