Topic 4 Lectorial.pdf

Topic 4 Lectorial – Peripheral Nervous System (8 cases) Cranial nerve testing Like reflex testing, cranial nerve testing is a simple, painless and non-invasive way to gain valuable information about the location of any nervous system damage or disease. The tests are...

Topic 4 Lectorial – Peripheral Nervous System (8 cases) Cranial nerve testing Like reflex testing, cranial nerve testing is a simple, painless and non-invasive way to gain valuable information about the location of any nervous system damage or disease. The tests are really testing the functions served by the cranial nerves rather than the nerves themselves, so they require both the nerves and the organs/ structures supplied by the nerves to be working. For example, to test the function of CN VIII, you check whether the subject can hear or not, taking each ear separately. Use your knowledge of cranial nerve functions to solve cases 1-5: Case 1 – Lop-sided mouth The people in the two pictures below are displaying the same cranial nerve problem. The woman is pictured with a neutral expression and the young man is pictured after he was asked to smile and close his eyes at the same time. What abnormalities are present? From this work out which cranial nerve on which side isn’t working for each individual? Eye Movements are controlled by six pairs of muscles (the extraocular muscles), which together allow us to roll our eyes around in every direction. Normally our eyes move together rather than independently, since we have binocular vision. The pairs of muscles moving the eyes are controlled by three different cranial nerves. Below is a diagram showing which cranial nerves supply which muscles. Use this information to answer the questions in cases 2 & 3. Case 2 - Wonky eye: This patient was asked to look straight ahead. Based on what you see, which cranial nerve is not functioning, and on which side? What other defects are likely to be present if this nerve is not functioning? Case 3 - Wonky eye: This patient was asked to look to his extreme right. Which cranial nerve is not functioning, and how would this person’s vision be affected? Case 4 – Abnormal tongue The patient in this picture was asked to poke her tongue out. Based on what you see, which cranial nerve is not working? Thinking about the extent of the abnormality, make an educated guess about how long the person has had this problem? Case 5 – Dicky heart If a person was experiencing cardiac arrhythmias due to a cranial nerve problem, which cranial nerve would it be? Case 6 – Shingles Shingles is caused by infection with the Herpes zoster virus. This virus causes chickenpox in children. The virus, however, remains in the body and can re-emerge in later life as shingles. The virus lives in the cell bodies of sensory neurons and when activated, can break out of the cell bodies and travel down the axons to cause a painful skin eruption. Below are some pictures of shingles eruptions. For each one, figure out which nerve the virus has travelled along to produce the lesions shown. What condition(s) would you think would encourage the virus to re- emerge and cause a new bout of shingles? Case 7 – Bike crash A young man was rushed into emergency after being thrown from his motorbike and landing on his head. He had suffered a cervical fracture at the level of C3, and died while being transported to hospital. What would have been the immediate cause of his death? Case 8 – Sore feet A 37 year- old man developed polydipsia and polyuria. Lab studies confirmed the diagnosis of diabetes mellitus and treatment with oral hypoglycemic drugs was started. Two months later he complained of an uncomfortable burning sensation in the soles of his feet, worse at night and not present when he walked. A neurological examination revealed no vibratory sense in the toes and reduced vibratory sense at the ankles, reduced pinprick and temperature sensation in the feet, absent ankle reflexes, and absent response to stimulation of the sole. His motor function was normal. Which type of neurons appears to have been affected by this problem? What response would you expect from scratching the sole of his foot? Why? What does this suggest? If his motor function was normal, why were his ankle stretch reflexes absent? The doctor informed the man that he had diabetic neuropathy, which was irreversible, but that there were some potential treatments for the pain he was experiencing at night. Diabetic neuropathy can affect somatic or autonomic neurons and sensory and motor neurons. It usually begins in the toes and can gradually ascend further up the body. It is the leading cause of mortality and morbidity in diabetic patients whose blood glucose has not been well controlled. Why would poorly controlled diabetes lead to polydipsia, polyuria and neuropathy?