Spinal dermoid sinus in a Dachshund with vertebral and thoracic limb malformations
© Barrios et al.; licensee BioMed Central Ltd. 2014
Received: 18 June 2013
Accepted: 24 February 2014
Published: 4 March 2014
Dermoid sinus is an uncommon epithelial-lined fistula that may be associated with vertebral malformations. In humans, Klippel-Feil syndrome (KFS) is a rare condition characterized by congenital cervical vertebral fusion and may be associated with other developmental defects, including dermoid sinus. The present case report describes an adult Dachshund with cervical and cranial thoracic vertebral malformations as well as thoracic limb malformations resembling KFS with a concurrent type IV dermoid sinus.
A 1.5 year-old Dachshund with congenital thoracic limbs deformities and cervical-thoracic vertebral malformations presented with cervical hyperesthesia, rigidity of the cervical musculature and tetraparesis. Neurologic, radiographic, and computed tomography (CT) (2D, 3D, CT fistulography) examinations revealed skeletal anomalies, a dermoid sinus in the cranial thoracic region and epidural gas within the vertebral canal. Surgical resection and histopathological evaluation of the sinus tract were performed and confirmed a type IV dermoid sinus. The clinical signs progressively recovered postoperatively, and no recurrent signs were observed after 6 months of follow-up.
Cervical vertebral malformations associated with limbs anomalies have not been reported in dogs and may represent a condition similar to KFS in humans. KFS can occur concurrently with other congenital conditions including dermoid sinus and should be included among the complex congenital anomalies described in dogs.
KeywordsDermoid sinus Klippel-Feil syndrome Limbs malformations Dog
Dermoid sinus (dermoid sinus tract, dermoid cyst, pilonidal sinus, or pilonidal cyst) is an uncommon developmental defect characterized by failed separation of the ectoderm and neuroectoderm during the early embryonic stage [1–3]. Dermoid sinus is generally benign: it occurs at the dorsal midline and connects the skin to deeper spinal structures, including the vertebral canal [1–4]. Spinal dermoid sinus occur as single or multiple lesions in the cervical, cranial thoracic, thoracolumbar, lumbosacral, and sacrococcygeal regions [5–9].
Craniovertebral or vertebral malformations (e.g. spina bifida, spinous process malformations, hemivertebrae, and block vertebrae) may be associated with congenital intracranial or spinal dermoid sinus [6, 12, 14–18]. Vertebral anomalies associated with limbs malformations are rare in small animals [19, 20]. In humans, congenital fusion and shortened cervical vertebrae (cervical synostosis) known as Klippel-Feil syndrome (KFS) is a congenital anomaly equivalent to block vertebrae observed in companion animals [21–24]. Klippel-Feil syndrome is caused by failed cervical somite segmentation during embryogenesis . However, KFS is usually associated with other multiple systemic anomalies such as scoliosis, visceral defects, deafness, and thoracic anomalies . This complex disorder may be observed concurrently with dermoid sinus and other neurological anomalies in humans. The present short communication describes an adult dog diagnosed with a type IV dermoid sinus, subtype a with axial and appendicular malformations, resembling a Klippel-Feil syndrome.
Postoperatively, 50 mg/kg/12 h PO sulfa and trimethoprim (Respig, Drag Pharma, Chile) for 30 days and 30 mg/kg/12 h PO metronidazole (Metronidazol L.CH., Laboratorio Chile, Chile) for 15 days were administered. Postoperative analgesia was administered with 2 mg/kg/8 h IV of tramadol (Tramadol, Biosano, Chile) and 2 mg/kg/24 h SC of carprofen for 2 days, followed by 2 mg/kg/12 h PO of tramadol (Tramal, Grünenthal, Chile) and 5 mg/kg/24 h PO of firocoxib (Previcox, Merial, Uruguay) for an additional 5 days. Several days postoperatively, a special cart was devised to provide thoracic support, which allowed the dog to walk freely. Two weeks postoperatively, pelvic limb movement and proprioceptive placing were improved, and no signs of cervical pain were observed. After 6 weeks, pelvic limb motor and sensory function were completely recovered, and no signs of cervical rigidity or cervical muscle spasms were present. The surgical site healed properly with no signs of infection.
The dog in the present case report suffered a congenital deformity characterized by cervical and cranial thoracic vertebral fusion (C2-C5 and T1-T2) and thoracic limbs abnormalities. These associated malformations have not been reported previously in dogs; whether these two concurrent malformations are part of a single syndrome in dogs remains unknown. Congenital cervical block vertebrae have been reported previously in dogs, but concurrent visceral or appendicular anomalies have not been observed . The axial skeletal anomalies (cervical block vertebrae) described in our report are similar to those of KFS in humans, which is a congenital fusion of two or more cervical vertebrae that may be associated with other organ system anomalies, including diffuse or focal thoracic limb hypoplasia [23, 25]. The dog in our study exhibited right thoracic limb hypoplasia, left thoracic limb amelia, and cervical vertebral body fusion consistent with KFS as described in humans.
Embryologically, the cervical spinal fusion results from failed mesodermal somites segmentation during the third and eighth weeks of gestation [23, 25]. Limbs form during the fourth week of gestation in dogs . In humans, the KFS anomaly is likely to develop during weeks 3–8 of gestation . Klippel-Feil syndrome is a complex developmental disorder, and its association with several other syndromes and/or anomalies suggests a basic skeletal disorder with spontaneous or genetic etiology. Genetic mutations in PAX1 and MEOX1 have been implicated in the KFS pathogenesis [27, 28]. These genes play important roles in somite development during embryogenesis in vertebrates. However, this syndrome likely has a heterogeneous etiology [27, 28].
In dogs, cervical vertebrae fusion and block vertebrae are usually incidental radiographic findings characterized by complete or partial fusion of two or more vertebral bodies, arches, or spinous processes . In dogs, cervical vertebral fusion anomalies are not clinically significant unless there is spinal instability or deformity, such as atlantoaxial instability, spinal stenosis, or angulation [24, 29]. However, no previous reports in dogs have associated cervical vertebral fusion defects with appendicular skeletal anomalies.
In humans, KFS is occasionally associated with dermoid or epidermoid cysts located at the cranium posterior fossa and rarely the cervical vertebrae [30, 31]. Additional neurological defects reported in KFS patients include diastematomyelia, syringomyelia, corpus callosum agnesis, meningocele, and cervical occult spina bifida, among others . Dermoid sinus and KFS may arise concurrently because both processes occur during the same developmental period. The separation of the neuroectoderm from the ectoderm occurs during the weeks 3–5 of gestation . Failure of this process results in cutaneous ectoderm sequestration, which forms the dermal epithelium and all skin appendages. The cutaneous ectoderm then migrates internally along with the folding of the neural tube forming a dermoid sinus [22, 26]. Cervical somite segmentation also occurs during the same period [22, 26]. In dogs and cats, dermoid sinus can be associated with vertebral anomalies, including block vertebrae, hemivertebrae, and partial fusion of vertebral arches (spina bifida) [6, 8, 12, 15, 18, 33, 34]. Spina bifida appears to be related to dermoid sinuses that extend to the vertebral canal [6, 8, 14, 33]. In this report, the dermoid sinus was located in the widened interarcuate spaces of the first thoracic vertebrae, as observed by 3D CT reconstruction. Dermoid sinuses can also reach the spinal cord by passing through osseous defects in the vertebral laminae or vertebral spinous processes . Abnormal tissue tension at the craniocervical segment secondary to abnormal flexure, vertebral fusion and cervical shortening associated with KFS has been proposed as the mechanism underlying ectodermal entrapment during neural tube closure [35, 36].
In humans and dogs with type IV dermoid sinus, meningitis or meningomyelitis may be caused by the infection from the fistulous tract via an opening between the skin and the dura mater or the skin and spinal subarachnoid space [8, 37, 38]. CSF or purulent discharge may be observed at the dermoid sinus orifice arising from the subarachnoid space . In the present report, a transparent viscous fluid discharge was observed at the dorsal midline skin orifice at T1-T2 three weeks prior to the clinical signs. Anorexia, resistance to cervical manipulation, cervical muscle fasciculations, and pelvic limbs proprioceptive deficits and weakness were considered signs of meningeal and spinal cord compromise . However, CSF could not be analyzed because the vertebral malformations made CSF extraction prohibitively difficult. Surgery revealed a type IV dermoid sinus connected to the meninges, which was not observed radiographically or on CT fistulography. Clinical signs of dermoid sinus can also result from by chronic spinal cord compression by the distended type IV dermoid sinus; in the absence of a subarachnoid communication epithelial tissue and debris accumulate in the distal and compress surrounding structures [8, 14]. In humans, meningitis, and intramedullary abscess have been documented in cases of spinal dermoid sinus [19, 38]. Bacterial culture from a swabbed dermoid sinus in dogs has shown mixed bacterial population predominated by Staphylococcus intermedius. Syringohydromyelia and tethering of the spinal cord has also been associated with canine dermoid sinus . Contamination and extension of the inflammation, infection, and/or chronic spinal cord compression from the dermoid sinus were most likely responsible for the neurological signs observed in this report.
Dermoid sinus is considered a hereditary neural tube abnormality in Rhodesian Ridgebacks [39, 40]. Their characteristic cutaneous ridge in this breed is an autosomal dominant mutation of fibroblast growth factor genes that predispose the animals to dermoid sinus [39, 40]. This developmental abnormality has been reported in several other breeds, including the American Cocker Spaniel, English Cocker Spaniel, English Springer Spaniel, Boxer, Chow-Chow, Golden Retriever, Shih Tzu, Siberian Husky, Yorkshire Terrier, German Shepherd, Rottweiler, Boerboel, Great Pyrenees, Swedish Vallhund, Chinese Crested, Victorian Bulldog, and occasionally in domestic cats [6–8, 11–14, 16, 17, 41–46]. No reports of dermoid sinus in Dachshunds were found in the literature.
The spinal emphysema, also known as pneumorrhachis, observed in the present case is an uncommon event in human patients and is usually associated with traumatic events, violent coughing, intradiscal gas accumulation, surgical or anesthesic manipulations, and iatrogenic etiologies . In dogs, intradiscal gas accumulation or the so-called “vacuum phenomenon” is a radiological finding that is observed in degenerative disc disease but has not been reported to produce or favor epidural gas accumulation . Potentially, communication between the exterior and the vertebral canal through the dermoid sinus fistula may have introduced air into the epidural space. The epidural space has an internal pressure bellow atmospheric pressure; therefore ambient air outside of the dermal orifice presumably follows gradient pressure forces towards the vertebral canal. Alternatively, this vertebral gas accumulation may be only an incidental finding [48, 49]. No previous description of epidural gas in human or animal patients diagnosed with dermoid sinus has been reported.
Cervical vertebral fusion defects associated with limb malformations have not been reported in dogs and may be manifestations of a similar condition in humans known as KFS. This rare and complex bone anomaly may be associated with other congenital conditions, including dermoid sinus, and should be included on the list of canine congenital anomalies. Additionally, this is the first report of spinal dermoid sinus in a Dachshund.
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