CT Myelogram to diagnose syrinx

[Karen]

My Dad is suffering with a neurological condition that despite exhaustive testing still does not have a name attached to it.  His physician, at a large teaching institution, thinks it may be a strange type of motor neuron disease or a syrinx, since his symptoms all seem to stop at the level of T-4. (He has a lot of sensory involvement in addition to the motor problems. Five doctors were in the room when he had EMGs/NCVs repeated last week and they were all scratching their heads.)  

He underwent a CT myelogram (not delayed) which failed to show anything though. (He cannot undergo MRI due to a pacemaker.)  And the physician feels that any syrinx causing the clinical symptoms that Dad has would be very large and would show up.  However, they did not do a delayed CT myelogram, which I understand is the preferred method for evaluation of a syrinx.  My questions are: 1. Should a delayed CT myelogram be performed?  2. Does the size of the syrinx really correlate with the patient's symptoms? From what I have read, they do not always.  Dad also went into respiratory failure about a month ago due to weakness of the diaphragm and intercostal muscles.  3. Would this mean that even if it was a syrinx, it would be too late to do anything to help him?

Thanks in advance for your kind and thoughtful answers.  You cannot imagine what a comfort it is to be able to find knowledgeable advice when dealing with such devastating diseases.

[CCF Neuro[P] MD, RPS]

Dear Karen:

I am not sure what you mean by delayed CT myelogram.  I think what you mean is a postmyelogram CT.  This is where the myelogram is done first followed by a CT, best performed with the patient in the supine postion.  This enables the contrast to pool in the anterior thecal sac and along the root pouches, making it most sensitive to root effacement by disk or bone.  Was there a problem with the CT? Or was it that your father could not tolerate the CT?  This is a good technique if your father can tolerate the lumbar puncture.  Was the CT with and without contrast non-informative?

The syrinx would have to be large to have both sensory and motor problems.  I would be suprised if the CT would not show a syrinx large enough to induce the symptoms you suggest your father has. The finding of a sensory and motor level at T4 suggest a spinal cord process. What was the etiology of your father's cardiovascular/respiratory arrest-pure motor atrophy or ???  Could your father have had a spinal infarct?  Why the pacemaker?  

Since your at a large teaching institution I assume that all my questions have been answered by the doctors.  Anyway, the myelogram followed by the CT would be a good test.

I hope that you find the answer to your father's condition.  

Sincerely,

CCF Neuro MD

[Karen]

In response to your questions: Dad has had a pacemaker for sick sinus syndrome for about 15 years.  The respiratory failure is due only to muscle weakness of the diaphragm and chest muscles-there is no underlying pulmonary disease.  He was able to tolerate the CT myelogram, which was done with and without contrast, but apparently if was not informative.  

From what I understand from some of the research I have been doing about this condition is that the best approach is to perform the myelogram, do the CT after injection and then 12 to 24 hours later also.  I would not want him to have to go through another myelogram if the first one would have been adequate to diagnosis a syrinx, but if it would be worth it to perform one and repeat the CT several hours later, I think he should. Also,would it be possible that since his symptoms have worsened so much since the first myelogram done several months ago, perhaps the syrinx is larger and would show up now?

Thanks so much for your help in understanding these very complex issues.

[CCF Neuro[P] MD, RPS]

Dear Karen:

If the syrinx is large enough to induce both sensory and motor changes it would be large enough to see on CT of the spine.  Having both symptoms and a distinct level on sensory exam, I would think that a process such as transverse myelitis or such would be in the diagnosis.  But, I am sure that they checked the CSF and found nothing to suggest a transverse myelitis and the CT with contrast would have shown something.

CCF Neruo MD