As noted, quadriparesis with reduced reflexes and difficulty with ventilator weaning may be seen as a result of a number of neuromuscular disorders. The clinical approach relies on exclusion of a central cause first, followed by careful examination of peripheral nerve and muscle function. Persistent neuromuscular blockade should be excluded initially because it is a readily reversible condition. Use of a train of four stimulation with a peripheral twitch monitor can quickly establish integrity of conduction across the neuromuscular junction. If necessary, further electrophysiologic studies allow differentiation among the relevant diagnostic possibilities. CIP is characterized by nerve conduction and EMG findings consistent with axonal degeneration of sensory and motor fibers. GBS is distinguished by evidence of demyelination on nerve conduction studies, in addition to elevated spinal fluid protein. Persistent neuromuscular blockade is identified by a decremental response on repetitive stimulation studies of neuromuscular transmission. The acute myopathy following neuromuscular blockage does not involve sensory responses. Needle EMG examination reflects a myopathic pattern, rather than a neurogenic one as seen in CIP or GBS. In myopathic patients who are unable to move their limbs at all (precluding a full EMG examination), a muscle biopsy identifies muscle as the site of involvement.