30 y.o. M PMHx hyperthyrodism, who presents c/o b/l leg weakness since this AM. Pt states he awoke with the symptoms and was unable to stand. Feels that his weakness is located in his thighs. Had similar episode 4 days ago, went to OSH and symptoms had resolved. Denies numbness, other neuro complaints, changes in bowel or bladder, trauma, history IVDU or CA, pain, fever, N, V, SOB.
meds: propylthiouracil, propanolol

Exam is significant for 1/5 strength to BL proximal  LE, with 5/5 strength distally. Sensation grossly intact. Somewhat hyporeflexic to lower extremities.

What tests would you order? What could be in the differential?

CBC wnl
BMP with K of 2.5
TSH low at 0.02
elevated free T4 at 3.69, T4 at 17.08 and T3 at 260.37

After ensuring that other diagnoses (cauda equina, epidural abscess, stroke, MG, etc.) are ruled out, given the above lab results one may entertain the possibility of periodic paralysis (PP). This patient had thyrotoxic PP.

– most common type of periodic paralysis is hypokalemic periodic paralysis. This should be differentiated from thyrotoxic PP (send labs). Less common is hyperkalemic PP.
– hypokalemic PP is a neuromuscular disorder (AD), defect in muscle ion channel
– episodes of painless muscular weakness
– usually affects proximal > distal, legs > arms, with hyporeflexia
– consciousness is preserved
– typically lasts several hours, but can be minutes to days
– may be precipitated by exercise, fasting, high-carb meals
– these activities release of epi or insulin -> K into cells
– K is normal between attacks (mean K 2.4 during attacks)
– replete gradually (10-30 meq/hr PO) and follow K, as there is potential for rebound hyperkalemia. Also, keep pt on monitor

 

Thyrotoxic PP:
– thyrotoxic PP can happen from any etiology of hyperthyroidism including meds
– may have mild myalgias. May have respiratory or bulbar weakness. May have fatal dysrhythmias.
– cases refractory to K may benefit from propanolol
– restoration of euthyroidism prevents/decreases attacks