Morphological Analysis and Osteometry of the Foramen Magnum of the One‐Humped Camel (Camelus dromedarius)

The foramen magnum (FM) has been an integral component of studies on the ontogeny and evolutionary transformation of the skull. While its shape is variable in different species and breeds, the morphological variations and metrical indices of the foramen have scarcely been studied in camels. A total of 30 adult camel heads with equal sex disparity from three different locations of Northern Nigeria were used in this study for determining the morphological characteristics and osteometry of their foramen magnum. The study reported a mean foramen magnum height and width of 4.04 ± 0.15 and 3.70 ± 0.16 cm, and 3.65 ± 0.27 and 3.45 ± 0.21 cm in the overall males and females, respectively, and a foramen magnum index (FMI) in adult camels, which was over 100. We propose a classification for the morphology of foramen magnum in camels demarcating them into three types. The dorsal border of the foramen presented either a smoothly curved bony margin (Type I), a small, ventrally directed, median bony protrusion (Type II) or a dorsal notch (Type III). No significant osteometric differences were found in any of the variables of the foramen magnum measured in the adult camels (FMH, FMW and FMI) of the various geographical locations, nor between animals of either gender except for the FMH that had a significantly higher mean value in overall males.     

Basicranial Analysis in Young Bovines Reveals a Relation to Breed and Sex

The purpose of this article was to examine the level of sexual dimorphism exhibited in the foramen magnum and occipital condyles of bovine juveniles and to test the utility of three basicranial measurements for estimating sex and to evaluate breed differences. Data were taken from 68 bovines of known sex, age and breed. The linear foramen magnum measurements (breadth and height) were not effective in determining the sex of the skulls, but there appeared differences of the occipital bicondylar breadth between sexes and breeds evaluated (‘Bruna dels Pirineus’ and others). The occipital bicondylar breadth assigned the sex correctly 75% of the cases. The study of occipital bicondylar breadth could thus be effective to obtain reliable results for the determination of sex in bovine skulls and also could be taken into account when differentiating breeds. It is considered that this study will make morphological contributions to develop a comparative model for other domestic bovine breeds, for there is inadequate literature on foramen magnum morphology for domestic species contrary to the richness of these kinds of studies on humans. The results obtained in this study can also be useful as baseline research data in comparative neuroanatomy and in neuropathology. Focusing on zooarchaeology and also on forensic veterinary, simple morphometric analysis of this type can be used as part of an investigative process prior to more sophisticated and expensive analyses such as the DNA examination.     

Dorsal notch of foramen magnum due to incomplete ossification of supraoccipital bone in dogs

The shape of the foramen magnum and the variation in the ossification pattern of the supra-occipital bone were studied in 48 skulls, including 12 from neonatal and 33 from immature and mature beagles of known age. The shape varied markedly, and a dorsal notch, dorsomedial to the nuchal tubercles and present in over half of the beagles, developed as a result of incomplete ossification of the ventromedial part of the supra-occipital bone. In a pomeranian and a chihuahua a membrane of dure mater and connective tissue, which covered the prominent dorsal notch, prevented prolapse of the brain. The spinal cord passed through a smaller oval opening in the ventral half of the foramen magnum. As there was no apparent impairment of function or anomalies associated with the dorsal notch and since a prominent dorsal notch was common in small breeds with brachycephalic skulls, it was concluded that the dorsal notch is a variation in the normal morphological pattern.     

Morphological investigations of the occipital area in adult American Staffordshire Terriers

Morphological investigations into the occipital area were carried out on the skulls of 24 adult American Staffordshire Terriers. The dorsal notch was found in one skull. The normal height (h) and width (W) of the foramen magnum was measured, and the foramen magnum index was calculated. In the case of the presence of the dorsal notch, total height (H) and normal height (h) of foramen magnum were measured, and dorsal notch height (N) was estimated. The mean value of the foramen magnum index (FMIa = W/H × 100) was 82.7. The foramen magnum index with the exception of the skull with dorsal notch (FMIb = W/h × 100) was 77.89. The dysplasia index (ISD = N/h × 100) was 44.05. A radiographic evaluation was made according to the method introduced by Rusbridge. Occipital dysplasia is not a clinical problem itself but can provoke one.     

Resolution of life-threatening dysphagia caused by caudal occipital malformation syndrome following foramen magnum decompressive surgery

A Cavalier King Charles Spaniel was presented with acute onset, life-threatening dysphagia suspected to be secondary to medulla oblongata compression caused by caudal occipital malformation syndrome. The patient required urgent tracheostomy tube placement to remain stable and was subsequently cured of the presenting neurological deficits by foramen magnum decompressive surgery. Neurogenic dysphagia is a relatively common presenting sign in human Chiari malformation syndromes, but has not been described as a major clinical sign in veterinary patients. Caudal occipital malformation syndrome should be included in the differential diagnosis list for susceptible breeds presenting with dysphagia. Early recognition favours expeditious surgical intervention and a positive outcome in human patients, and this may also be the case in veterinary patients.     

CHARACTERISTICS OF CEREBROSPINAL FLUID FLOW IN CAVALIER KING CHARLES SPANIELS ANALYZED USING PHASE VELOCITY CINE MAGNETIC RESONANCE IMAGING

Syringomyelia is an important morbidity source in Cavalier King Charles Spaniels. Although abnormal cerebrospinal fluid (CSF) flow secondary to Chiari malformations is thought to cause syringomyelia in humans, this relationship is unknown in dogs. We used phase-contrast magnetic resonance (MR) imaging to evaluate CSF flow in dogs. Fifty-nine Cavalier King Charles Spaniels were assigned a neurologic grade reflecting their neurologic status. Five normal control dogs of other breeding were imaged for comparison. The presence of syringomyelia was noted from sagittal MR images. The pattern and velocity of CSF flow were assessed using phase-contrast cine MRI at the foramen magnum, C2–C3 disc space, and within syrinxes. Flow was measured most easily with the neck flexed to mimic standing. CSF flow velocity in the dorsal aspect of the subarachnoid space at the foramen magnum was significantly higher in control dogs than Cavalier King Charles Spaniels ( P =0.035). Flow was obstructed at the foramen magnum in 41 of 59 Cavalier King Charles Spaniels. Turbulent flow and jets were associated with syringomyelia presence and severity, and CSF flow velocity at C2/3 dorsally was inversely related to the presence of syringomyelia ( P =0.0197). Peak dorsal subarachnoid space CSF flow velocity at the foramen magnum and C2–C3 were together highly predictive of syringomyelia. CSF flow can be assessed in dogs using phase-contrast cine MRI. Obstruction to flow at the foramen magnum is common in Cavalier King Charles Spaniels and CSF flow pattern and velocity are related to the presence of syringomyelia.     

MAGNETIC RESONANCE FOR EVALUATION OF NEUROLOGIC DISEASE IN 12 HORSES

Magnetic resonance (MR) imaging was used as a neurodiagnostic modality in the assessment of 12 horses with neurologic disease localized cranial to the foramen magnum. This retrospective study included a mixed population of horse breeds and consisted of three foals and nine adult horses. MR sequences of the head and central nervous system of each horse were acquired. Routine MR sequences included transverse T1 weighted (T1wt), T2 weighted (T2wt), and proton density images. Additional imaging sequences were obtained on a patient-dependent basis. Eight neurologic related diseases were diagnosed. MRI imaging of the horse head is a feasible and valuable neurodiagnostic modality in the assessment of equine neurologic diseases.     

Morphological analysis of the foramen magnum of dogs from the Iron Age

The investigations were carried out on 37 skulls from the Van-Yoncatepe early Iron Age necropolis (in eastern Anatolia) (first group) and 11 skulls from the scythians castle from Bileskoje Iron Age (second group). The major distance between both occipital condyles and both bases of the jugular processes, the major width of the foramen magnum, height of the foramen magnum, height of the skull, height of the occipital triangle and the length of the dorsal notch were measured. A dorsal notch was present in seven dogs (six male and one female) from Van-Yoncatepe. The average length of the dorsal notch was 2.5 mm. The investigation states that the dorsal notch occurred in dogs from the Iron Age. This anatomical formation had no association with their death.     

A study on morphology and morphometric parameters on skull of the Bardhoka autochthonous sheep breed in Kosovo

In this study, we aim to investigate the skull of Bardhoka sheep, which is the native breed of Kosovo by utilising normal morphometric methods. Differences between male and female were also statistically analysed. Further, the parameters that can be used in gender discrimination were also analysed. The statistical analysis was based on a sample of 24 adult skulls of Bardhoka breed with 12 female and 12 male skulls. Altogether, 31 different measurements were taken morphologically and 7 different indices were applied. Except for the measurement's values of the orbit, measurement's values of length of the cheek tooth row and the measurement's values of height of the foramen magnum, all the measured values of males were higher than females. Nasal index, cranium index and skull index values were statistically significant between both genders. It is envisaged that the findings of this study will motivate and assist other comparative studies with other autochthonous sheep and goat breeds found in the Dukagjini region or in clinical veterinary practice and even in zooarchaeology.     

Magnetic resonance imaging,clinicopathologic findings,and clinical progression of a puppy with confirmed Eastern equine encephalitis virus

A 5-month-old puppy was evaluated for rapidly progressive neurologic signs and pyrexia. Magnetic resonance imaging showed multifocal meningoencephalitis with transtentorial and foramen magnum herniation. A cerebrospinal fluid tap revealed highly cellular fluid, and the puppy was euthanized. Histopathology showed lymphoplasmacytic and neutrophilic meningoencephalitis. Viral polymerase chain reaction testing for Eastern equine encephalitis was positive. Rapid progression of neurologic signs and respiratory arrest necessitated mechanical ventilation. Severe hypernatremia, most consistent with central diabetes insipidus, developed.Key clinical message:Transtentorial and foramen magnum herniation and high cerebrospinal fluid cell counts may be indicators of poor prognosis. Brain death, respiratory arrest, and central diabetes insipidus may also ensue with Eastern equine encephalitis infection.     

Osteological features in pure-bred dogs predisposing to thoracic or lumbar spinal cord compression

Consistent with those vertebral sites most commonly clinically affected by spinal cord compression, body size normalised midsagittal diameters of the caudal vertebral foramen limits T10-T12 were significantly (P<0.05) lower in Dachshunds relative to other breeds. Minimal midsagittal diameters in Yorkshire Terriers and Maltese were noted at T11cd/12cr. However, these diameters were always larger (P<0.05) in small breeds compared to those in Dachshunds and large breeds suggesting that the small breeds investigated are at lower risk of developing clinical signs if a compressive disease occurs at that site. In large breeds, minimal values were present at L1cd/L2cr and in agreement with clinical findings correlate with those spinal sites most susceptible to spinal cord compression in nonchondrodystrophic large breeds. Caudal displacement of the lumbosacral enlargement of the spinal cord relative to the position previously noted in large breeds was confirmed for the Dachshunds and 50% of small breeds. However, caudal displacement was also noticed in the German Shepherd dogs.     

Foramen magnum decompression for treatment of caudal occipital malformation syndrome in dogs

A method for foramen magnum decompression (FMD) in dogs with caudal occipital malformation syndrome (COMS) and results for 16 dogs are described. In brief, a dorsal approach to the caudal portion of the occiput and arch of the atlas was made, and a high-speed drill was used to remove a portion of the occiput in the region of the foramen magnum and the dorsal aspect of C1. The meninges that were exposed were removed or marsupialized to surrounding tissues. Foramen magnum decompression was performed in 16 dogs. No intraoperative complications occurred, and postoperative complications occurred in only 2 dogs after initial surgery and in 1 of these dogs after follow-up surgery. In both dogs, postoperative complications after the initial surgery resolved without additional treatment. One dog was nonambulatory tetraparetic after follow-up surgery and died of a suspected ruptured viscus 9 days after surgery. Four dogs developed evidence of scar formation at the surgery site and required additional surgery. Overall, 14 dogs survived, 1 died, and 1 was euthanatized. Clinical signs resolved in 7 of the 14 dogs that survived, improved in 6, and did not change in 1. Results suggest that FMD may be an effective treatment for dogs with COMS, especially if performed early in the course of the disease.     

Morphometric analysis of the skull of Hamdani sheep via Three-Dimensional modelling

The aim of the present study was to determine the craniometric characteristics of the crania of Hamdani sheep, one of local breeds of Turkey, by using computed tomography (CT). In the study, 13 (six female and seven male) skulls were used. After CT images of the skulls were taken, their three-dimensional models were created by MIMICS 20.1 (The Materialise Group, Leuven, Belgium) program. Thirty-eight craniometric measurements were taken over the models created and nine indices were calculated by using these measurements. All the characteristics examined were expressed as mean ± SE. In the study, statistically significant differences were found between females and males in terms of greatest neurocranium breadth, facial breadth, greatest palatal breadth (p < 0.05) and height of the foramen magnum (p < 0.01) parameters. No statistically significant difference was observed between the sexes in the calculated index values (p > 0.05). In conclusion, it is thought that the findings obtained from the study will contribute to the zooarchaeology and sheep taxonomy of Mesopotamian region.     

Cerebellar vascular hamartoma in a British Shorthair cat

Cerebellar vascular hamartoma was diagnosed in a 16-month-old cat following magnetic resonance imaging and incisional biopsy. The clinical features were consistent with the cerebellar site of the lesion accompanied by signs attributable to cerebellar herniation through the foramen magnum and increased intra-cranial pressure. A lesion of this type represents a previously unreported differential diagnosis for central nervous system lesions in young cats.     

Ultrasonographic appearance of the craniocervical junction in normal brachycephalic dogs and dogs with caudal occipital (Chiari-like) malformation

Ultrasonographic evaluation of the spine, especially of the spinal cord, has been rarely reported in dogs. The atlanto-occipital junction provides a small acoustic window through which examination of the craniocervical transition can be performed. Normal sonographic findings of this region in 10 normal brachycephalic dogs are presented and compared with sonographic findings from 25 Cavalier King Charles Spaniels with the caudal occipital malformation syndrome. Sonographic findings were compared with magnetic resonance imaging findings to determine the extent of cerebellar herniation and syringohydromyelia. Cerebellar displacement into the foramen magnum was clearly identified sonographically; however, syringohydromyelia was not discernable due to bone overlay.     

RADIOGRAPHIC ANATOMY OF THE DROMEDARY SKULL

Radiographs were made of the skull of a 1.5-year-old and a 3-year-old camel for the purpose of assessing and describing the radiographic anatomy. Radiographic anatomy was compared with results from gross dissection of 5 additional camel specimens. Camel skull anatomy was related to that of the horse and ox. Obvious differences were found. These include in the camel, large occipital condules, a notched foramen magnum, an intracranial projection for the interparietal bone, and small paranasal sinuses. Other minor differences are detailed in the text.     

Morphological and Experimental Studies on the Development of the Posterior Wall of the Avian Foramen Magnum

In embryos of Gallus, Anas and Sphentscus the posterior wall of the foramen magnum (tectum synoticum) is formed by the fusion of the two independently developing supra-occipital cartilages. Fusion of the supraoccipital cartilage with the ear capsule precedes that between the supraoccipital cartilage and the occipital process. The supraoccipital cartilage intervenes between the occipital process and the ear capsule before fusion of these elements occurs. In Gallus the tectum synoticum is secondarily fused to the supracapsular cartilage.     

IDENTIFICATION OF ARACHNOID CYSTS IN THE QUADRIGEMINAL CISTERN USING ULTRASONOGRAPHY

The ultrasonographic findings in three small breed dogs with intracranial arachnoid cysts are described. Ultrasound images were obtained via the foramen magnum, temporal window and persistent bregmatic fontanelle (when possible). In transverse, dorsal and sagittal transcranial ultrasound images there was marked dilation of the lateral ventricles and a well-defined, oval to triangular-shaped anechoic area between the caudal aspect of the occipital lobes, dorsal to the midbrain, and rostral to the cerebellum. These findings were consistent with a diagnosis of concurrent hydrocephalus and an arachnoid cyst within the quadrigeminal cistern.     

The course of the nasolacrimal duct in brachycephalic cats

Casts of the nasolacrimal duct system were obtained from 50 euthanised cats including brachy-, meso- and dolichocephalic breeds. The course of the nasolacrimal duct, which was assessed radiographically and gross-anatomically, was strongly related to the shape of the skull. In meso- and dolichocephalic cats the nasolacrimal duct formed a dorsally opened arch with the descending part being directed rostroventrally. The main part of the duct passed the nasal cavity in a rather horizontal course parallel to the hard palate and was located ventrally to the lacrimal foramen. However, foreshortening of the face was associated with a right-angled or even acute-angled alignment of the duct. In higher degrees of brachycephaly the main part of the duct ascended beyond the level of the lacrimal foramen and passed the nasal cavity dorsal to the level of the lacrimal foramen. This specific course of the nasolacrimal duct in brachycephalic cats was consistent with a steeper alignment and attachment of the maxilloturbinate. Accessory orifices of the nasolacrimal duct opening into the nasal cavity had never been observed. The present results strongly suggest that the specific course of the nasolacrimal duct in brachycephalic cats might hinder the drainage of the lacrimal fluid irrespective of the diameter of the lumen of the nasolacrimal duct system.     

Syringohydromyelia in Cavalier King Charles spaniels

Syringohydromyelia secondary to foramen magnum overcrowding is described in seven Cavalier King Charles spaniels. Clinical signs were consistent with a central spinal cord lesion. The most common signs were persistent scratching at the shoulder region with apparent neck, thoracic limb, or ear pain and thoracic limb lower motor neuron deficits. The diagnosis was made by magnetic resonance imaging. The syringohydromyelia is postulated to be a consequence of an occipital bone malformation resulting in a small caudal fossa and cerebellar herniation. Clinical signs improved but did not completely resolve when the dogs received treatment with corticosteroids or nonsteroidal anti-inflammatory drugs.