20 terms

neuro clinical correlations lec 23-27

shingles (herpes zoster)
following an attack of chickenpox the herpes virus may become latent in dorsal root ganglion cells (or trigeminal ganglion cells), reactivation of the virus produces painful skin irritations in the dermatomal area innervated by the related ganglion
Brown Sequard syndrome
hemisection of the spinal cord as a result of a slow growing mass or a traumatic lesion interrupting ascending and descending fibers on one side of the cord

touch, vibration and proprioception are lost on one side of the body whereas pain and temperature are lost on the other side of the body

at the level of the lesion, on the side of the lesion, have loss of sensations for touch,, vibration, proprioception, pain and temperature

below level of lesion on same side of lesion have sensory loss of touch, vibration, and proprioception for all dermatomes below

below the level of lesion on opposite side of lesion, pain and temperature sensations are lost, starting one or two segments below lesion and including all dermatomes below
a pathological enlargment of central canal of spinal cord, can be due to cyst in anterior white commissure

as cavity expands it interrupts fibers that cross through the anterior white commisure, interrupts anterior lemniscus system-->bilateral lost in pain and temperature
tabes dorsalis
clinical syndrome which is the consequence of a syphilitic infection, destruction of dorsal root ganglion cells with large diameter myelinated axons causes severe deficit in touch and proprioception

nociception and temperature sense remain almost unaffected
phantom limb sensations
following the amputation of a limb the patient often feels sensations which seem to orginate from the missing limb, usually sensation of pain (neuropathic pain--deafferentation pain)

likely explanation is reorganization of cortical maps, may be rearrangement or cortical input to area that formerly represented amputated limb

ex for amputated hand, touch pathways originating in face are likely to form new circuits within the primary somatosensory cortex (S1) that connect them with cortical neurons that would have otherwise become "jobless" (lacking innervation from the missing limb)-->phantom limb sensation evoked by touching face
caused by stimulation of pain-sensitive structures like the wall of blood vessels, the dura mater, and the periost

no nociceptors in the brain
effect of aspirin and other non-steroidal anti-inflammatory analgesics in controlling pain is due to its ability to inhibit the enzyme cyclo-oxygenase responsible for the synthesis of prostaglandins--agents which sensitize sensory afferent fibers
according to NIH and the Mayo Clinic, acupuncture may offer symptomatic relief for a variety of diseases and conditions including low back pain, headaches, fibromyalgia, migraines and osteoarthritis

research shows acupuncture can help manage postoperative dental pain and alleviate chemotherapy-induced nausea and vomiting

appears to offer relief for chronic menstrual cramps and tennis elbow

acupuncture release opioid peptides, the secretion of hypothalamic pituitary neurotramsitters and neurohormones, and alterations in immune function
strong pain killers, used for more serious pain conditions, activate physiological pain control circuitries by binding to opioid receptors

ex. morphine,
surgical management of pain
used when all measures aimed at direct causes of pain have been exhausted

ie to relieve otherwise intractable pain such as in terminal cancer patients

ex. dorsal rhizotomy, ie transection of dorsal roots of the spinal nerves
the focus of parallel lights (far vision) is anterior to the photosensitive elements of the retinal photoreceptors, objects positioned closer to the eye (near visioin) can still be focused on the retina even without the contribution of the usual mechanisms for near accommodation

vision is best during near vision, nearsightedness, treat with corrective lenses or corneal surgery
the focus of the parallel light rays (far vision) is beyond the retina, objects in the far distance from the eye can still be brought into focus by activating the mechanisms for near accommodation which increase the refractive power of the eye

near accommodation fails for objects close to the eye and reduces the ability for near vision

vision is best during far vision, farsightedness, treat with corrective lenses or corneal surgery
describes the state of vision where an object at infinity is in sharp focus with the eye lens in a neutral or relaxed state, this condition of the normal eye is achieved when the refractive power of the cornea and the axial length of the eye balance out, which focuses rays exactly on the retina resulting in perfect vision

an eye in a state of emmetropia requires no correction
optic disk edema, important clinical sign which can indicate increased intracranial pressure, increased pressure compromises the venous drainage of the eye leading to dilation of the retinal veins, as a consequence the optic disc is pushed forward and the disk appears white rather than pink as in normal conditions

seen when inspecting the ocular fundus with an ophthalmoscope
detached retina
the retina separates from teh retinal pigment epithelium and the areas detached lose their function

a focal lesion in a defined region causes a scotoma

laser surgery can stop the process of further separation although the detached part of the retina does not regain ts function
age related macular degeneration (AMD)
patients have poor central vision but most can walk, dress themselves, and perform many normal daily tasks

leading cause of vision loss in individual age 60+ years of in US and many European countries

genetic, ocular and environmental factors, age, smoking and body mass index heavily contribute to the incidence of AMD
diabetic retinopathy
patients suffering from diabetes mellitus are associated with increased blood glucose levels and retina vulnerability

the retinal defects are caused by blood supply dysfunction including reduction of permeability of basal membranes of capillary endothelial cells and blood vessel damage (aneurysms)

during the initial phase of diabetes smaller scotomas are usually not recognized by the patient, as soon as the macula is involved the visual loss increase dramatically
retinitis pigmentosa
a group of serious, mostly genetically determined (autosomal dominant, autosomal recessive, X-linked) degenerative diseases in which rods preferentially degenerate

one of the earliest symptoms is night blindness followed by loss of peripheral vision leading to tunnel vision

a progressive disease which can lead to total blindness,

accumulation of pigment can be seen through the opthalmoscope

photoreceptor degeneration is often associated with reduced phagocytosis by retinal pigment epithelium (RPE) cells during process of disk shedding
night blindness (nyctalopia
encountered in individuals with vitamin A deficiency

vitamin A is the precursor of retinal (vitamin A aldehyde) which together with the opsin protein forms the photoreceptor pigment
color blindness
due to a lack of a particular cone type, most common is red-green color blindness inherited by an X-linked recessive gene, appearing more frequently in male subjects

individuals affected by red-green color blindness can no longer distinguish certain red colors from certain green colors

two different types of red-green color blindness:
protanopia--L cone (red cone) absent--affecting 1.3% of males
deuteranopia--M cone (green cone) absent--affecting 1.2% of male

S cone (blue cone) deficits are rare