Head drop in neurologic disease: differential and pearls

Clinical: typically occurs in women over age 65
neck extensor weakness is usually subacute and associated with proximal arm weakness

EMG abnormal (myopathic or denervating) in cervical or thoracic paraspinal muscles but normal in limb muscles

Immunomodulators don't affect prognosis

differential:
polymyositis
ALS  (usually not isolated finding)
MG   ( three percent have headdrop as initial presentation)

 IBM
CIDP
carnitine deficiency
FSH
myotonic dystrophy
congenital myopathy
hpt
Parkinson's disease

Briemberg-Use of MRI-- in MG signal from paraspinals is normal, in isolated myopathy of neck muscles there is edema seen.The MG would be seronegative myasthenia gravis.