Dr Simona Radaelli
DVM PhD DipECVN MRCVS
RCVS and European Specialist in Veterinary Neurology
“Daisy” is a 10 yr FN Collie cross. She presented with sudden onset neurological signs. Her owner reports that she has been drooling a lot this morning. She didn’t want any breakfast today.
Work through the quiz to reach the diagnosis.
1) How would you describe Daisy’s head posture?
Correct – the ears are on a vertical line, with one held lower than the other, so there is rotation of the median plane of the head.
Incorrect – the nose is turned towards the shoulder, but the ears would be on a horizontal line if this was a head turn.
Incorrect – pleurothotonus refers to head and body turn and this patient only has head involvement. Pleurothotonus is often due to a cerebral lesion.
2) Is the abnormal head posture right-sided or left-sided?
Correct – the head is tilted towards the left.
3) Where in the nervous system would you localize the lesion?
Incorrect – head turn and pleurothotonus are more common with a forebrain lesion.
Cervical spinal cord
Incorrect – lesions to the cervical spinal cord normally do not affect the head positioning as in the photo. Low head carriage is more common with cervical spinal cord lesions.
Correct – this abnormal head position occurs due to the loss of extensor muscle tone on one side of the neck – the left side of the neck in this case – due to the malfunction of the left vestibular system; the normal right extensor muscles ‘push’ the head to the left side.
4) What other neurological signs would you expect?
Seizures, abnormal proprioception, abnormal mentation
Incorrect: these signs are more common with a forebrain lesion.
Spontaneous nystagmus, strabismus, +/- abnormal proprioception
Correct: spontaneous horizontal nystagmus usually has a slow phase (towards the affected side) and a fast phase (towards the normal side). Strabismus is normally ventrolateral with a vestibular disorder. Abnormal proprioception is present with a lesion of the central vestibular system. Other signs like vomiting or salivation are less common in dogs and often present only in the very acute phase of the vestibular dysfunction.
Abnormal proprioception, reduced withdrawal in the forelimbs, neck pain
Incorrect: these signs are more common with a cervical spinal cord lesion.
5) What main clinical sign will help you to distinguish between a central nervous system and a peripheral nervous system lesion in this case?
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Abnormal proprioception – deficits in postural reactions would indicate a central lesion. This is because the proprioceptive pathways are in the brainstem.
6) Commonly, would you expect this clinical sign to be ipsilateral (towards) or contralateral (away from) to the lesion?
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Ipsilateral – the head tilt is nearly always ipsilateral to the lesion. In rare cases of central vestibular syndrome, the head tilt can be opposite the side of the lesion-this is called paradoxical vestibular syndrome-in these cases the lesion will be on the same side as the proprioceptive deficits.
7) What gait abnormality would you expect in this case?
Correct – vestibular ataxia, usually manifested as leaning and falling to one side.
8) What are your main differential diagnoses for an elderly patient presenting with these signs? Try to divide them in to peripheral and central disease.
Idiopathic, neoplasia (tumour of the middle/inner ear), metabolic (hypothyroidism), inflammatory (otitis media/interna).
Neoplasia (brain tumours), vascular (cerebrovascular disease), inflammatory (meningoencephalitis), toxic (metronidazole).
9) Which of the following diagnostic plans would be most appropriate?
Haematology and biochemistry, MRI of the brain, CSF tap.
Haematology and biochemistry, Otoscopy, MRI of the brain, CSF tap.
Correct – otoscopy is important to rule out middle ear involvement.
MRI of the cervical spinal cord, CSF tap.
Electrodiagnostics (Electromyography (EMG) and nerve conduction velocity (NCV)
10) If you suspected a peripheral nervous system lesion, what could be performed instead of the MRI?
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CT scan can help evaluating middle ear disease as the resolution of this area of the skull is very good; it is not very useful when evaluating the caudal fossa, where the central vestibular system is located: due to beam hardening artifacts the details of the brainstem are not as clear as with the MRI.