Surgical treatment of tethered spinal cord syndrome in a dog with myelomeningocele

Open spina bifida characterisation in a dog foetus

BACKGROUND

Open spina bifida is an uncommon malformation in animals, and there is a lack of imaging, clinical, and pathological characterisation of this condition in dogs.

OBJECTIVE

Open spina bifida is rarely observed in animals due to high levels of perinatal mortality and frequent euthanasia. To the best of our knowledge, we present the first case of spina bifida in a dog was diagnosed in-utero and then followed post-partum.

METHODS

A 3-year-old Poodle was presented with twin pregnancy. Radiographic and ultrasonographic findings were suggestive of vertebral malformation and open spina bifida with myelomeningocele in one foetus. Conservative treatment was given but the puppy died 3 days after birth. Thereafter, anatomical and histopathological analysis of several organs was performed to characterise the disease.

RESULTS

When the twins were born, one puppy had a linear dorsal midline cutaneous defect extending from the level of vertebrae L2-L6. R Radiographic examination showed several congenital vertebral malformations involving the thoracic segment, lumbar segment, sacrum and scapula. Histopathological examinations confirmed the presence of open spina bifida and identified additional abnormalities in several internal organs.

CONCLUSIONS

This case presents a complete characterisation of open spina bifida, before birth and after death, using imaging and histopathology techniques.

Association between filum terminale internum length and pain in Cavalier King Charles spaniels with and without syringomyelia

Background

Lumbar syringomyelia (SM), lumbosacral pain, and more caudal spinal cord termination are reported in Cavalier King Charles spaniels (CKCS). Data are lacking on the clinical relevance of alterations in their spinal cord terminal structures.

Objectives

To compare spinal cord termination level and filum terminale internum length (FTIL) with presence of lumbar SM and clinical signs in CKCS.

Animals

Forty‐eight CKCS.

Methods

In this prospective study, pain was quantified using owner and clinician assessments. Vertebral level of spinal cord and dural sac termination, presence of SM, and FTIL were determined from sagittal magnetic resonance imaging (MRI) sequences. Kappa and intraclass correlation (ICC) analyses determined interobserver reliability. The MRI findings were compared to owner and clinician‐reported pain quantification.

Results

Interobserver reliability was good for spinal cord and dural sac termination (kappa = 0.61 and 0.64, respectively) and excellent for FTIL (ICC: 92% agreement). The spinal cord terminated at 6th lumbar vertebra in 1, 7th lumbar vertebra in 31, and the sacrum in 15 dogs, and termination level was associated with lumbar SM (P = .002) but not clinical signs. Mean FTIL was 2.9 ± 1.08 mm; it was associated with owner‐reported pain (P = .033) and spinal palpation scores (P = .023). Painful CKCS without SM had shorter FTIL compared to normal CKCS and painful CKCS with SM (P = .02).

Conclusions

Painful CKCS without SM have decreased distance between the termination of the spinal cord and dural sac, suggesting a shorter FTIL. More caudal spinal cord termination is associated with development of lumbar SM.

Comparison of inherited neural tube defects in companion animals and livestock

Neural tube defects (NTDs) are congenital malformations resulting from the improper or incomplete closure of the neural tube during embryonic development. A number of similar malformations of the protective coverings surrounding the central nervous system are also often included under this umbrella term, which may not strictly fit this definition. A range of NTD phenotypes exist and have been reported in humans and a wide range of domestic and livestock species. In the veterinary literature, these include cases of anencephaly, encephalocele, dermoid sinus, spina bifida, and craniorachischisis. While environmental factors have a role, genetic predisposition may account for a significant part of the risk of NTDs in these animal cases. Studies of laboratory model species (fish, birds, amphibians, and rodents) have been instrumental in improving our understanding of the neurulation process. In mice, over 200 genes that may be involved in this process have been identified and variant phenotypes investigated. Like laboratory mouse models, domestic animals and livestock species display a wide range of NTD phenotypes. They remain, however, a largely underutilized population and could complement already established laboratory models. Here we review reports of NTDs in companion animals and livestock, and compare these to other animal species and human cases. We aim to highlight the potential of nonlaboratory animal models for mutation discovery as well as general insights into the mechanisms of neurulation and the development of NTDs.

Neural tube defects in four Shetland sheepdog puppies: clinical characterisation and computed tomography investigation

BACKGROUND

Here, we report on the occurrence of neural tube defects (NTDs) in four related Shetland sheepdog puppies. NTDs present as a range of congenital malformations affecting the spine, skull and associated structures. Despite the severity of these malformations and their relatively high prevalence in humans, the aetiology is not well understood. It is even less well characterised in veterinary medicine.

CASE REPORT

Affected puppies were investigated using computed tomography (CT) and then necropsy. CT identified a range of brain and spine abnormalities in the affected animals, including caudal anencephaly, encephalocele, spina bifida and malformed vertebrae. Other observed abnormalities in these puppies, including cranioschisis, atresia ani and hydrocephalus, may be secondary to, or associated with, the primary NTDs identified.

CONCLUSION

This case report describes multiple related cases of NTDs in an Australian cohort of dogs. This study also highlights the potential of advanced imaging techniques in identifying congenital anomalies in stillborn and neonatal puppies. Further research is required to investigate the aetiology of NTDs in this group of affected Shetland sheepdogs.

Surgical outcomes of six bulldogs with spinal lumbosacral meningomyelocele or meningocele

OBJECTIVE

To report the surgical treatment and outcome of six bulldogs with spina bifida (SB) and meningocele (MC) or meningomyelocele (MMC).

STUDY DESIGN

Case series.

ANIMALS

Five French bulldogs and one English bulldog with MC or MMC.

METHODS

Medical records of dogs with spinal MC or MMC diagnosed by MRI at two institutions between 2013 and 2016 were reviewed for surgical treatment and outcomes.

RESULTS

Meningocele was diagnosed in two dogs, and MMC was diagnosed in four dogs. A lumbosacral dimple was noted in all dogs along with neurological deficits most commonly consisting of urinary and fecal incontinence (n = 6) and mild/moderate paraparesis (n = 3). Dorsal laminectomy was performed in all dogs to allow dissection of the meningeal sac to the vertebral column defect. In dogs with MMC, nerves were repositioned and protruded meninges were removed prior to suturing remaining meninges. Adhesions and filum terminale were resected in two dogs with suspected tethered cord syndrome. Urinary and fecal incontinence improved in two dogs and remained unchanged in four. Paraparesis improved in two dogs.

CONCLUSION

Surgical treatment resulted in partial improvement of the urinary and fecal incontinence (2/6 dogs) and paraparesis (2/3 dogs) or stable neurological condition (3/6 dogs), with only minor temporary complications.

CLINICAL SIGNIFICANCE

In the absence of published data comparing surgical and conservative treatment of puppies affected by SB and MC or MMC, early surgical treatment can be considered to prevent deterioration of neurological signs and, eventually, facilitate improvement of neurological signs.

Variation in the position of the conus medullaris and dural sac in adult dogs

Although it has long been stated that the level of spinal cord termination varies depending on the size of the dog, the evidence for this remains limited. The aim of this study is to investigate the position of the conus medullaris (CM) and dural sac (DS) in a population of dogs of varying size. MRIs of the thoracolumbosacral spine of 101 dogs were included. The location of CM and DS was determined on sagittal T2-weighted images and T1-weighted images, respectively, by three independent observers. The bodyweight and the back length were used as markers of size. Regression analysis showed that the termination point of the CM had a statistically significant relationship with bodyweight (R²=0.23, P<0.05). Although not statistically significant (P=0.058), a similar relationship was found between CM and back length (R²=0.21). No statistically significant relationship was found between the termination point of the DS and bodyweight (P=0.24) or back length (P=0.19). The study confirms the terminal position of the CM is dependent on size, with a more cranial position with increasing size; however, the termination point of DS remains constant irrespective of dog size.

Congenital malformations of the lumbosacral vertebral column are common in neurologically normal French Bulldogs, English Bulldogs, and Pugs, with breed-specific differences

Congenital vertebral malformations are common findings on diagnostic imaging of the vertebral column in "screw-tailed" brachycephalic dogs. The aims of this study were to evaluate the prevalence and anatomical characteristics of lumbosacral congenital vertebral malformations in French Bulldogs, English Bulldogs, and Pugs presenting for problems unrelated to spinal disease, as well as possible associations with the degree of tail malformation, lumbosacral intervertebral disc herniation, or spondylosis deformans. In this retrospective cross-sectional study, CT scans of vertebrae L6 to S3 and of the coccygeal vertebrae were reviewed for type of congenital vertebral malformations (hemivertebrae, block vertebrae, lumbosacral transitional vertebrae, and spina bifida), lumbosacral intervertebral disc herniation, lumbosacral spondylosis deformans, and degree of tail malformation. In 76 (51.0%) of the 149 included dogs (53 French Bulldogs, 37 English Bulldogs, and 59 Pugs) at least one type of congenital vertebral malformations was found, with lumbosacral transitional vertebrae being the most common (34.2%). There was a significantly higher prevalence of lumbosacral transitional vertebrae (54.2%) and lower prevalence of hemivertebrae (1.7%) in Pugs compared to English (13.5% and 24.3%, respectively) and French Bulldogs (26.4% and 32.0%, respectively). Tail malformation was significantly more severe in dogs with evidence of hemivertebrae. Congenital vertebral malformations are a common finding in the lumbosacral vertebral column of French Bulldogs, English Bulldogs, and Pugs. These anatomical variances need to be considered when interpreting diagnostic studies and when planning for neurosurgical and neurodiagnostic procedures. Furthermore, this study suggests a possible association between the degree of tail malformation and lumbosacral hemivertebrae.

Dermoid sinus type VI associated with spina bifida and tethered cord syndrome in a French Bulldog

A 4-mo-old French bulldog was presented with acute onset pain and reluctance to move. A tubular structure arising in the dorsal thoracic midline and extending from a cutaneous orifice into deeper tissues was palpated on physical examination. Computed tomography with sinography revealed a dermoid sinus associated with spina bifida at the level of T3-T4. On surgical exploration, the dermoid sinus was found to communicate with the dura. Histology confirmed the diagnosis and classification as a type VI dermoid sinus. The pain response and hyperesthesia were suspected to be the result of tethered cord syndrome. Complete resolution of clinical signs was appreciated post-surgery, with the patient still free of clinical signs 3 mo later.

Morphometric analysis of spinal cord termination in Cavalier King Charles Spaniels

BACKGROUND

There is an association between Chiari malformations, syringomyelia (CMSM) and tethered cord syndrome (TCS) in people, suggesting Cavalier King Charles Spaniels (CKCS) with CMSM could also have TCS. Currently there are no data on the position of the caudal spinal cord structures in CKCS.

OBJECTIVE

To describe and compare location of spinal cord termination in CKCS with weight-matched controls and to examine the relationship between SM and spinal cord termination.

ANIMALS

Thirty-nine CKCS and 33 controls with thoracolumbar MRIs; 34 of 39 CKCS also had cervical MRIs.

METHODS

Blinded retrospective study. Spinal cord and dural sac termination were determined from T2-weighted sagittal and transverse images and half-Fourier acquisition single-shot turbo spin echo sequences. Intra-observer reliability was determined using kappa analysis. Presence of SM was compared with location of spinal cord and dural sac termination.

RESULTS

Intra-observer reliability was moderate for identifying spinal cord termination (Kappa = 0.6) and good for dural sac termination (Kappa = 0.8). The spinal cord terminated at lumbar vertebra 6 (L6) in 1, 7 (L7) in 22, and sacrum in 16 CKCS versus 9 at L6, 23 at L7, 1 at sacrum in controls. Spinal cord (P < .001) and dural sac (P = .002) termination were significantly more caudal in CKCS compared to controls. The presence of thoracolumbar SM was associated with more caudal dural sac termination in CKCS (P = .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

The relationship between TL SM and possible spinal cord tethering because of a more caudal dural sac termination should be investigated.

Tethered cord syndrome with spina bifida aperta in cats: two case reports of different types

CASE SUMMARY

Two castrated male cats, aged 8 months old (case 1) and 10 months old (case 2), showed a history of progressive paraparesis, an over-reaching pelvic limb gait, urinary incontinence and a palpable dermoid fistula. In case 1, the fistula was connected to the dural sac on the conus medullaris, and the tethered spinal cord was retracted caudally. In case 2, the tubular structure was connected to the dural sac on the thoracic spinal cord, and the tethered spinal cord was retracted dorsally. Tethered cord syndrome secondary to spina bifida aperta was suspected in both cats. Excision of the fistula and release of the tethered spinal cord was performed. A histopathological examination confirmed the diagnosis of a meningomyelocele in case 1 and a meningocele in case 2. Paraparesis improved postoperatively in both cats. However, urinary incontinence in case 1 remained partially unresolved.

RELEVANCE AND NOVEL INFORMATION

This is the first report to describe the imaging characteristics, surgical treatments and outcomes of two different types of tethered cord syndrome with spina bifida aperta in cats. Tethered cord syndrome with spina bifida aperta needs to be included in the differential diagnosis of slowly progressive paraparesis in younger cats with or without vesicorectal failure and a palpable dermoid fistula.

Spina Bifida, Meningomyelocele, and Meningocele

Spina bifida with or without meningocele or meningomyelocele is encountered infrequently in small animal practice. The English bulldog and Manx cat are breeds predisposed. Although often silent clinically, in those animals with clinical signs, it is important to recognize the signs early and to understand the appropriate imaging modalities employed in establishing a diagnosis. In a select population of affected animals, proposed surgical intervention may be considered to prevent neurologic decline, prevent secondary complications, and potentially improve outcomes.

Surgical correction of a sacral meningomyelocele in a dog

A 15 wk old male unilateral cryptorchid German shepherd dog weighing 18 kg was referred for a nonhealing cutaneous lesion dorsally at the level of the sacrum, urinary incontinence, and a deviated tail. MRI revealed spina bifida and meningomyelocele continuous with the skin surface. Surgical correction of the meningomyelocele involved closure of the open meningeal defect, transection of the abnormal spinal nerves to the skin surface, and closure of the skin defect with a good outcome. Histopathology confirmed a meningomyelocele. This case report describes the MRI findings, surgical procedure, and proposed pathogenesis of spina bifida and meningomyelocele in a dog.

MRI of a split cord malformation in a German shepherd dog

A 9 yr old spayed female German shepherd dog was referred for MRI of the thoracic and lumbar spine because she had clinical signs of chronic neurogenic bladder dysfunction of an unknown cause. Transverse T2-weighted images identified a type II split cord malformation (i.e., diastematomyelia) in the thoracic spine. Split cord malformations are forms of spinal dysraphism where the abnormal development of spinal cord results in sagittal splitting of a portion of the cord into two hemicords. The location of the lesion in the thoracic spine was consistent with the dog's clinical signs of an upper motor neuron bladder. Split cord malformations that occur in humans have similar MRI characteristics and can result in similar clinical signs as those identified in the dog described in this report.

MRI findings, surgical treatment and follow-up of a myelomeningocele with tethered spinal cord syndrome in a cat

A 7-month-old male neutered cat was referred for paraparesis and painful sensation at the level of T13 vertebra where a dermal cyst was observed. Spine radiographs and magnetic resonance imaging (MRI) showed a well-encapsulated cyst communicating with the meninges and spinal cord, suggestive of hydromyelia and myelodysplasia. Dorsal laminectomy was performed and the cyst was completely removed. The day after surgery, the cat was ambulatory paraparetic. Involuntary defecation was observed for only a few days. The surgical specimen was cystic and covered by skin. Microscopic examination revealed a hollow hemispheric mass of glial fibrillary acidic protein (GFAP)-positive neural tissue lined by ependyma and formed of glia and vascular structures consistent with myelomeningocele (MMC). Only anecdotal descriptions of MMC have been published in the veterinary literature, mainly in the lumbosacral spinal cord. To the authors' knowledge, this is the first report of a MMC with tethered spinal cord syndrome in a cat successfully treated surgically.