Chiari-Like Malformation/Syringomyelia (Caudal Occipital Malformation Syndrome/Occipital Hypoplasia)
An anatomical abnormality of the occipital bone. Typically, the ventral aspect of the occipital bone is malformed and replaced by a membranous band of tissue. Oftentimes, the caudal aspect of the cerebellum and the dorsal aspect of the cranial cervical spinal cord and a caudal brainstem are exposed. It remains controversial whether this abnormality is associated with clinical signs. However, it has been proposed that fluid-filled cavities in the spinal cord, such as syringomyelia or hydromyelia, are secondary to abnormal pulsation of cerebrospinal fluid within or around the foramen magnum.
Age of Onset: Few months to 4 years of age is most common, although any age of dog can be affected
Sex Predisposition: Any sex of animal can be affected, however in some reports there were more females than males included.
Clinical Course:
Clinical signs can vary from mild to severe clinical dysfunction. Similarly, the clinical course can vary from short with recovery, progressively worsening impairment, or waxy and waning clinical signs.
Clinical Signs:
Behavioral/Mental Awareness
Vocalization/ vocalization when people greeting the dog
Vocalization when scratching
Vocalization when defecating
Aversion to the ears/head/neck being touched or groomed
Sleep disruption
Acting timid or anxious
Becoming withdrawn
Scratching or rubbing of the head or ears
Aggression
Licking of a limb
Sleeping with an elevated or unusual head posture
Repetitive barking
Exercise intolerant
Posture and Appearance
Scoliosis/Cervicothoracic torticollis
Abnormal head/neck posture when awake
Movement
Changes in activity/movement
Refusal/hesitation/difficulty climbing stairs or jumping
Thoracic limb hypermetria
Ataxia (of the limbs)
Hypermetria or other exaggerated movements (of the limbs)
Proprioception
Conscious proprioceptive deficit (of the limbs)
Muscle Atrophy
Thoracic limb muscle atrophy
Pain Sensation
Pain in or around the spine
Refusal to rise to greet, or no longer greeting
Aversion to the sternum or flank being touched or groomed
Apparent pain involving the face
Aversion to limb/paw being touched/groomed
Clinical signs can vary from mild to severe clinical dysfunction. Similarly, the clinical course can vary from short with recovery, progressively worsening impairment, or waxy and waning clinical signs.
Clinical Signs:
Behavioral/Mental Awareness
Vocalization/ vocalization when people greeting the dog
Vocalization when scratching
Vocalization when defecating
Aversion to the ears/head/neck being touched or groomed
Sleep disruption
Acting timid or anxious
Becoming withdrawn
Scratching or rubbing of the head or ears
Aggression
Licking of a limb
Sleeping with an elevated or unusual head posture
Repetitive barking
Exercise intolerant
Posture and Appearance
Scoliosis/Cervicothoracic torticollis
Abnormal head/neck posture when awake
Movement
Changes in activity/movement
Refusal/hesitation/difficulty climbing stairs or jumping
Thoracic limb hypermetria
Ataxia (of the limbs)
Hypermetria or other exaggerated movements (of the limbs)
Proprioception
Conscious proprioceptive deficit (of the limbs)
Muscle Atrophy
Thoracic limb muscle atrophy
Pain Sensation
Pain in or around the spine
Refusal to rise to greet, or no longer greeting
Aversion to the sternum or flank being touched or groomed
Apparent pain involving the face
Aversion to limb/paw being touched/groomed
Spinal (cervical); Intracranial (possibly/periodically)
Unknown
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