Neupsy Key

Aside from the olfactory cranial nerve (CN I) and the optic nerve (CN II), the remaining cranial nerves (CN III–XII) have nuclei in the brainstem. These then have axons extending…

The muscle stretch, or “deep tendon,” reflex is the product of a segmental reflex arc involving specific spinal cord or brainstem regions; this makes testing reflexes useful for anatomic localization….

Temperature and pain sensations are conveyed via small myelinated and unmyelinated nerve fibers. These enter the spinal cord via the dorsal spinal root and synapse in the dorsal horn at…

Fasciculations are caused by spontaneous depolarization of lower motor neurons, which results in contraction of the muscle fibers in the associated motor unit. Clinically this manifests as a visible twitch…

Unilateral foot drop is a common complaint. Careful examination of the anatomical pattern of the weakness helps identify the most likely location of the causative lesion. In some cases, clinical…

The quadriceps muscles in the anterior thigh extend the knee and are innervated by the femoral nerve, which arises from the lumbar plexus. The L2, L3, and L4 nerve roots…

Unilateral hand numbness is a common complaint with multiple potential causes. Careful examination of the anatomical pattern of the numbness helps identify the most likely location of the causative lesion….

Careful examination of the anatomical pattern of unilateral hand weakness helps identify the most likely location of the causative lesion. In some cases, clinical weakness is subtle and the pattern…

Wrist drop refers to an impairment in hand extension at the wrist. There is usually concurrent finger extension weakness (“finger drop”). The most common localizations are peripheral processes, such as…

Symmetric proximal weakness is most commonly associated with primary muscle disease (myopathy). However, diseases of the neuromuscular junction, neuropathies, spinal cord disease, and very rarely cerebral infarction can produce similar…