7yo Golden with hindlimb weakness and elevated CK

Thanks for the consult on this Golden. The combination of hindlimb weakness and an elevated CK is a very helpful pointer, but before we jump to a diagnosis, we must neurolocalize. The CK elevation strongly suggests muscle disease (myopathy) or a severe neuropathy causing secondary muscle damage, but we need the exam to confirm.

"Where is the lesion?" Let's walk through the possibilities based on what a full neurological exam would show.

Neuromuscular Pattern (Most Likely): This is my primary suspicion. You'd see diffuse lower motor neuron (LMN) signs.

* Gait: Short-strided, stiff, may look like they are walking on eggshells. Weakness may be worse in the hindlimbs but thoracic limbs are often subtly affected too.
* Reflexes: Spinal reflexes would be decreased to absent in all four limbs.
* Muscle Tone: Decreased (flaccid).
* Other: No ataxia, normal mentation, normal cranial nerves. Palpation of major muscle groups might elicit pain.

Lumbosacral (L4-S3) Pattern: If the signs are truly restricted to the pelvic limbs.

* Gait: LMN paraparesis. Weak, scuffing hindlimbs.
* Reflexes: Decreased to absent patellar and withdrawal reflexes in the pelvic limbs. Normal reflexes in the thoracic limbs.
* Other: May have decreased tail tone or a large, easily expressed bladder. Less likely to cause a profound CK elevation unless the onset was extremely acute and traumatic.

Differential Diagnosis & Plan

Given the signalment and high CK, a primary myopathy is at the top of my list. My differential list, in order of probability, would be:

Inflammatory Myopathy (Polymyositis): An immune-mediated inflammation of the muscles. Goldens are a predisposed breed. This fits the clinical picture perfectly.

Infectious Myositis: Consider protozoal causes like Neospora caninum or Toxoplasma gondii.

Endocrine Myopathy: Hypothyroidism can cause a myopathy and/or neuropathy. A 7-year-old Golden is in the classic age range.

Paraneoplastic Myopathy: Underlying neoplasia (e.g., lymphoma, thymoma) can trigger an immune response against muscle.

Recommended Next Steps:

Confirm Localization: Perform a full neurological exam to confirm if this is a diffuse neuromuscular problem. Pay close attention to thoracic limb reflexes.

Bloodwork: If not already done, submit a full thyroid panel (T4, free T4, TSH) and infectious disease titers (Neospora, Toxoplasma).

Advanced Diagnostics: The definitive workup for a suspected myopathy involves:

* Electromyography (EMG) & Nerve Conduction Velocity (NCV): This will confirm myopathic changes (spontaneous activity in muscles) and rule out a primary neuropathy.
* Muscle Biopsy: This is the gold standard. A biopsy from a moderately affected muscle (e.g., cranial tibial or triceps) for histopathology will confirm polymyositis and rule out other causes.

Staging: Perform thoracic radiographs and an abdominal ultrasound to screen for underlying neoplasia.

The high CK is your guide here—it's pointing you away from the spinal cord and directly toward the muscles. A thorough exam will solidify that suspicion, and then EMG with muscle biopsy will give you the definitive answer.

Let me know what your full exam reveals.