What do people mean by "neck weakness", and what does it feel like?

Need more info. Neck weakness can be a laxity of neck muscles and difficulty w/ holding up or turning head. Possible causes include: •motor neuron disease, guillian barre syndrome, myasthenia gravis, hyperparathyroidism, carnitine deficiency, myotonic dystrophy, spinal muscular atrophy, trauma or injury or pinched nerve...To list a few.