An increase in height of the medial longitudinal arch of the foot that does not flatten on weight bearing (i.e., a distinctly hollow form of the sole of the foot when it is bearing weight).

Hyperextension of the metatarsal-phalangeal joint with hyperflexion of the proximal interphalangeal (PIP) joint.

A type of hearing impairment in one or both ears related to an abnormal functionality of the cochlear nerve.

A decreased magnitude of the sensory perception of sound.

A shaky or wobbly manner of walking.

Absence of neurologic reflexes such as the knee-jerk reaction.

An anomaly of visually evoked potentials (VEP), which are electrical potentials, initiated by brief visual stimuli, which are recorded from the scalp overlying the visual cortex.

An abnormality of the auditory evoked potentials, which are used to trace the signal generated by a sound, from the cochlear nerve, through the lateral lemniscus, to the medial geniculate nucleus, and to the cortex.

The term gait disturbance can refer to any disruption of the ability to walk.

Reduction of neurologic reflexes such as the knee-jerk reaction.

A reduction in the number of axons in the peripheral nervous system.

A segmental pattern of demyelination and regeneration (remyelination) affecting peripheral nerves.

An abnormal reduction in sensation in the distal portions of the extremities.

Repeated episodes of segmental demyelination and remyelination lead to the accumulation of supernumerary Schwann cells around axons, which is referred to as onion bulb formation. This finding affects peripheral nerves.

A decrease in the ability to perceive vibration in the distal portions of the limbs.

A type of Developmental delay characterized by a delay in acquiring motor skills.

A reduction in the speed at which electrical signals propagate along the axon of a neuron.

A reduced sense of touch (tactile sensation) on the skin of the distal limbs. This is usually tested with a wisp of cotton or a fine camel's hair brush, by asking patients to say 'now' each time they feel the stimulus.

A loss or impairment of the sensation of the relative position of parts of the body and joint position occurring at distal joints.

A lack of strength of the proximal muscles.

Reduced strength of the musculature of the distal extremities.

An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane.

Muscular atrophy affecting muscles in the distal portions of the extremities.

An abnormality of the hand characterized by metacarpophalangeal (MCP) hyperextension and proximal interphalangeal (PIP) and distal interphalangeal (DIP) flexion. The position of the affected hand is said to resemble a claw.

Glaucoma refers loss of retinal ganglion cells in a characteristic pattern of optic neuropathy usually associated with increased intraocular pressure.

Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment.\n\nNearsightedness usually begins in childhood or adolescence. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). In some people, nearsightedness improves in later adulthood.\n\nFor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. People who are nearsighted typically have eyeballs that are too long from front to back. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. It is this change that causes distant objects to appear blurry. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be.\n\nNearsightedness is measured by how powerful a lens must be to correct it. The standard unit of lens power is called a diopter. Negative (minus) powered lenses are used to correct nearsightedness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. In an individual with nearsightedness, one eye may be more nearsighted than the other.\n\nEye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. These problems include tearing and detachment of the retina, clouding of the lens (cataract), and an eye disease called glaucoma that is usually related to increased pressure within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye.

Curvilinear intracellular accumulation of autofluorescent lipopigment storage material within axons.