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Patient History:  A 10 year 6 month old dachshund was presented to the Veterinary Neurological Center for evaluation of episodic neck pain and progressive difficulty using the left thoracic limb for the past 2 months.  The patient had shown brief periods of transient improvement with cage rest and administration of Rimadyl® and occasional tramadol.

Question:  Based on this radiograph and the presenting signs, where would the problem most likely be localized?