Lumbosacral L5-S1 plexopathy?

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latinman

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60 y/o male with complaint of unilateral left lower extremity burning pain x 2 years. Starts in his buttocks and the pain goes to his knee. Pt denies any trauma, falls, weakness or atrophy. The pain is worse when he tries to elevate the left leg, standing, or bending. Pt denies any weight loss. Pt with minimum back pain. (+) shopper's cart sign. The neurontin seems to help with the pain

Physical Exam:
SLR negative both legs.
Reflexes: Absent Left achilles reflex , and 2+ Right achilles.
Bilateral patella symmetrical.
Sensation from L4-S1 dermatome about the same.


Strength-weak left hip flexor 4- vs right 4-5.

5/5 bl knee extensors/flexors. 4-/5 on left dorsiflexion and 4+-5 on right.

R EHL 4-5. left EHL impaired due to h/o toe fusion. Weak FHL on right 4- to 4+, and Left FHL impaired 2ry fusion.


NCS Results:

30 % difference on the AH tibial motor side to side. The left side slightly slower.

> 50% difference on the EDB motor side to side. Lower on the left side (2.5 vs 5).

No difference on bilateral TA motor side to side.

Left Sural SNAP was absent and completely present on the right (7 to 8 uV).

Left Sup Peroneal SNAP was slightly lower (4-5) than the right Peroneal SNAP (6-7) but within 50%.


Hreflex absent on the left leg, and normal on the right (~32).

Limited Needle EMG of left Gastroc, TA, and Left L5/S1 paraspinals was clean.

I know how I should have considered EMG of the TP, EDB, Gluteus Medius or Maximus.

At this point my question is whether you would consider Pelvic Imaging for this patient.

MRI Lspine showed mod-severe DJD throughout lumbar disc, central canal stenosis L2-3, and L4-5 due to disc bulge. Mod-severe foraminal stenosis L5-S1.
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Any butt/piriformis tenderness to palpation? His altered foot mechanics from his toe fusion might be causing problems higher up the biomechanical chain, actually resulting in the dreaded piriformis syndrome.
 
I didn't palpate his buttock. But if you are considering piriformis syndrome (and indirectly compression of the sciatic nerve) shouldn't his tibialis anterior on the left side be abnormal compared to the right, since it is peroneal innervated and as a result coming from the sciatic nerve? I was thinking more about L5/S1 plexus lesion for that reason. I may be wrong.

Actually both Dx are fair game in this kind of situation. The toe fusion could definitely alter his biomechanics the same way a morton neuroma or something else would.

Some people think that piriformis syndrome is wastebasket diagnosis.
 
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Sounds like proximal sciatic nerve, piriformis syndrome high on the list. I don't find MRI finds much in these cases, but I get them anyway. Intersting that he has hip felxor weakness - antalgic?

Try a piriformis or sciatic block and see what the response is.
 
I agree, sound like S1>L5. That sural and the clean paraspinals are suspicious for a plexus/sciatic lesion. I would agree that more needle exam might be worthwhile. Unless you needle exam was limited due to patient factors vs time constraints etc. If he had symptoms for 2 years he might have all chronic neuropathic MUAPs and no Ps and fibs, proximal muscles and side-side comparision for amplitude/duration/recruitment might give you a little more insight. He has fairly impressive MRI findings...I guess I wouldn't jump to pelvic imaging unless he had a h/o of a pelvic trauma, had cancer, or has never seen a doctor except for you and you're worried about a cancer.

He also has bilateral, distal weakness on his exam, the left is a little more impressive, did he have anything to suggest an asymmetric polyneuropathy? NCS-wise things sounded pretty normal on the right though and doesn't fit the history.
 
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