Kin 411: Lecture 12

What is Herpes Zoster (aka Shingles)? What are it's symptoms (3)?

Shingles is a sensory disorder caused the reactivation of chicken pox virus that was previously lying dormant in the dorsal root ganglions (this is important to know, bc that's where the sensory neuron cell bodies are). The reactivated virus will travel down a sensory nerve and will show up in the skin supplied by that nerve.

Sx:

1. Shingles cause ipsilateral rashes following one dermatome. It does NOT cross the midline.

2. Allodynia and paresthesias along specific dermatome

3. Sometimes pain lasts much longer tho, this is post herpetic neuralgia

Post herpetic neuralgia

Long term pain sensation from herpes zoster (shingles)

What is Tabes Dorsalis? What are it's symptoms?

Tabes Dorsalis is late-stage untreated neurosyphilis (for at least 10-30 years) that progessively destroys the dorsal (posterior) columns, dorsal roots and ganglia of the spinal cord, typically in the lumbar region

Symptoms:

1. Loss of proprioception (d/t damage of dorsal columns)

2. Paresthesias (d/t ^^)

3. Allodynia

4. Tabetic Gait to compensate for lack of proprioception: high steppage, foot flapping, wide stance, knee locked

What is neuropathy?

A nerve disorder that may affect/influence the function of axons, myelin, or both.

1. Damage to axons affect what function? 2. What about myelin?

1. The ability for signals to travel

2. The speed at which the signal travels, OR how the signal travels (e.g., distortion of how signals travel lead to inapprioprate sensations like tingling, burning, and weakness where that shouldn't happen)

What is mononeuropathy? Give an example!

1. A condition by which only one nerve is affected. These conditions are usually more localized and specific.

2. Example: Carpal tunnel syndrome

What is a polyneuropathy? Give 4 examples

A condition that results from multiple effected nerves and is generalized/widespread

Examples:Diabetes, overdose of pyridoxine (Vitamine B6), ganglionopathies, and polyneuritis

Diabetic neuropathy. Effects/Sx/Cause

a. Diabetes:

- typically affects the distal limbs

- “Glove and stocking” pattern of sensory loss

- Symptoms:

• Allodynia: d/t ALP damage

• Paresthesias: d/t PCML damage

Cause :

• High glucose levels: neurotoxic

  • Leads to inflammation of nerves

  • poor blood supply to those small nerves

Vit B6. Sx/Cause

Overdose of Pyrodoxine (Vitamin B6)

- Symptoms: severe proprioceptive loss, sensory ataxia, delayed postural response

- Cause: overdose of Vitamin B6 leading to degeneration of the large, myelinated Ia afferents

Ganglinopathies

c. Ganglinopathies:

- Doral root ganglion damage (by extension, also sensory neuron cell bodies)

-Symptoms: issues with standing/walking w/o visual input since no proprioception or cutaneous input

-Causes : dorsal root ganglia damage * note this is very similar to Tabes Dorsalis

Polyneuritis. Cause? Sx?

Polyneuritis (random hint: wherever you see -itis, that means inflammation)

- Polyneuritis is inflammation of many nerves that may be caused by autoimmune disorders, infections, or toxins

- Symptoms: sensory loss, pain, and weakness.

3 major functions of the vestibular system

• maintenance of balance

• muscle tone (primarily extensor tone, remember VST)

• eye muscle control / reflexes

where is the vestibular system

• within the inner ear, colocated with the auditory system

• inner ear is embedded in / carved out of the petrous ridge of the temporal bone

Top to bottom

1. Middle fossa

2. Petrous ridge of temporal bone

3. Posterior fossa

Vestibular system is made of what kind of labyrinths?

the vestibular system is made up of the bony labyrinth and the membranous labyrinth

What is bony labyrinth carved out of

petrous ridge of temporal bone

Bony lab is filled with ____ which surrounds the _____ ____ which is filled with ____

Bony labyrinth is filled with perilymph fluid which surrounds the membranous labyrinth which is filled with endolymph fluid

What is membranous lab made up of?

1. Semi circular canals

2. Utricle and saccule (2 large swellings)

It’s floating in perilymph fluid

Location of utricle vs saccule

The saccule is adjacent to the cochlea

Utricle is what all the semi canals are coming out of (like bagpipe)

top to bottom

perilymph fluid

endolymph fluid

Left to right clockwise

Posterior semi canal

Horizontal semi canal

Bony labyrinth

Membranous labyrinth

Anterior semi canal

Utricle

saccule

the 3 semi-circular canals and their orientation

1. Anterior (goes about 45 degrees out and forward)

2. Posterior (goes about 45 degrees out and to back)

3. Horizontal / Lateral (roughly parallel to horizon)

all orthagonal to each other (all 90 degrees apart)

specify which semi-circular canals are parallel to each other on left and right side

• left horizontal and right horizontal

• left anterior and right posterior

• left posterior and right anterior

What is the ampulla?

One side of each semi canal bulges to form the ampulla adjacent to the utricle

Left to right clockwise

Endolymph flow

Ampula

Cupula

Cilia

Hair cells
Crista ampullaris

Axons to vestibular ganglion

crista ampularis

ridge of epithelial cells that form the floor of the ampulla

hair cells are embedded in the ___and have ___projecting out from them to

crista ampullaris; cilia; embed in the cupula

What is cupula

Gelantinous mass that is attached to the crista ampularis and goes up to the roof of the ampulla

What happens when endolymph flows thru ampula?

Cupula deflects and moves, moving the cilia encased with it

hair cells within the cupula are activated as a _____

population

The two types of cilia that make up the hair cells

Kinocilum: thick and stiff, one per receptor

Stereocilia: flexible, moves as population, organized in descending order as they move away from kino

Stereocilia moving towards kinocilium leads to? away from kinocilium? (3 each)

depolarization, excitation and increased firing rate

hyperpolarization, inhibition, and decreased firing rate

Where do axons from hair cells go?

Axons from hair cells project down to cell bodies in the vestibular ganglion