Neurology: Nerve Degeneration

Question 1

What are featuresof motor neuron disease?

Answer 1

• Neurological condition of unknown cause which can present with both upper and lower motor neuron signs.
• Rarely presents before 40 years and various patterns of disease are recognised including amyotrophic lateral sclerosis, progressive muscular atrophy and bulbar palsy

Question 2

How does Amyotrophic Lateral Sclerosis present?

Answer 2

• Affects both upper (corticospinal tracts) and lower motor neurons
• Results in a combination of upper and lower motor neuron signs

Question 3

What are signs and symptoms of Motor Neuron Disease?

Answer 3

• Fasciculations
• Absence of sensory signs/symptoms (vague sensory symptoms may occur early in the disease e.g. limb pain but ‘never’ sensory signs)
• Mixture of lower motor neuron and upper motor neuron signs
• Wasting of the small hand muscles/tibialis anterior is common
• Doesn’t affect external ocular muscles
• No cerebellar signs
• Abdominal reflexes are usually preserved and sphincter dysfunction if present is a late feature

Question 4

What are investigations for Motor Neuron Disease?

Answer 4

Diagnosis of motor neuron disease is clinical

• Nerve Conduction Studies: show normal motor conduction and can help exclude a neuropathy.
• Electromyography: Shows a reduced number of action potentials with increased amplitude.
• MRI: Performed to exclude the differential diagnosis of cervical cord compression and myelopathy

Question 5

What is Duchenne muscular dystrophy?

Answer 5

• Duchenne muscular dystrophy there is a frameshift mutation in Dystrophin gene resulting in one or both of the binding sites responsible for sturcture or binding of muscles
• Progressive proximal muscle weakness from 5 years

Question 6

What are signs and symptoms of Duchenne’s Muscular dystrophy?

Answer 6

• Calf pseudohypertrophy
• Gower’s sign: child uses arms to stand up from a squatted position
• 30% of patients have intellectual impairment

Question 7

What are Dystronopathies?

Answer 7

• X-linked recessive due to mutation in the gene encoding dystrophin, dystrophin gene on Xp21.
• Dystrophin is part of a large membrane associated protein in muscle which connects the muscle membrane to actin, part of the muscle cytoskeleton
• Includes Becker Muscular Dystrophy and Duchenne’s Muscular Dystrophy

Question 8

How can diabetes causes Neuropathies?

Answer 8

• High blood sugar can injure nerves throughout your body and mostly damages nerves in your legs and feet. It can be disabling and quite painful
• May affect as many as 50% of people with diabetes

Question 9

What are symptoms of Diabetic Neuropathy?

Answer 9

• Peripheral Neuropathy
  
  • Numbness and reduced ability to feel pain or temperature changes
  • Tingling or burning sensation
  • Sharp pains or cramps
  • Increased sensitivity to touch
  • Serious foot problems such as ulcer, infections and bone/join pain
• Autonomic neuropathy
  
  • Lack of aware of low blood sugar levels
  • Bladder or bowel problems
  • Slow stomach emptying causing nausea, vomiting and loss of apetite
  • Changes in the way your eyes adjust from light to dark
  • Decreased sexual response
• Proximal neuropathy (diabetic polyradiculopathy)
  
  • Severe pain in hip, thigh or buttock
  • Eventual weak and shrinking thigh muscle
  • Difficulty rising from sitting position
  • Severe stomach pain
• Mononeuropathy (focal neuropathy)
  
  • Difficulty focusing or double vision
  • Aching behind one eye
  • Paralysis on one side of your dace (bell’s palsy)
  • Numbness or tingling in your hand or fingers except your little finger
  • Weakness in your hand that may cause you to drop things

Question 10

What are the risk factors of Diabetic Neuropathy?

Answer 10

• Poor blood sugar control
• Diabetes history
• Kidney disease: leads to toxin in blood damaging nerves
• Being overweight: increase risk of diabetic neuropathy
• Smoking: narrows and hardens arteries reducing blood flow to legs and feet

Question 11

What are complications of Diabetic Neuropathy?

Answer 11

• Hypoglycaemia unawareness
• Loss of toe, foot or leg
• Urinary tract infections and urinary incontinence
• Sharps drops in blood pressure
• Digestive problems
• Sexual dysfunction
• Increased or decreased sweating

Question 12

How is Diabetic Neuropathy prevented?

Answer 12

• Blood sugar management
• Foot care
  
  • Check your feet everyday
  • Keep your feat clean and dry
  • Moisturize your feet
  • Trim your toenails carefully
  • Wear clean and dry socks
  • Wear cushioned shoes that fit well

Question 13

What is the causes of Subacute combined degenration of spinal cord?

Answer 13

• Combined cord and peripheral nerve damage is sequel of Addisonian pernicious anaemia and rarely other causes of B12 deficiency.
• Nitrous oxide abuse may cause functional B ₁₂ deficiency.

Question 14

What are symptoms and signs of Subacute combined degeneration of the spinal cord?

Answer 14

• Numbness and tingling of fingers and toes
• Distal sensory loss particularly of the posterior column
• Absent ankle jerks
• Cord involvement leading to exaggerated knee jerks and extensor plantar
• Optic atrophy
• Retinal haemorrhage
• Sphincter disturbance, severe generalized weakness and dementia may develop in later stages

Question 15

What are investigations of subacute combined degeneration of the spinal cord?

Answer 15

• Activated vitamin B₁₂ , methylmalonic acid and homocysteine levels should be checked.
• Macrocytosis with megaloblastic marrow

Question 16

What is the treatment for Subacute combined degeneration of the spinal cord?

Answer 16

• Parenteral B₁₂ reverses nerve damage but has little effect on the cord and brain.

Question 17

What is Syringomyelia?

Answer 17

• Syringomyelia is a fluid-filled cavity within spinal cord and often associated with Arnold-Chari malformation. Cases associated with Arnold-Chiari malformation usually develop symptoms around age 20-30 years of age
• Syrinx is in continuity with central canal of the cord. May also allow spinal cord trauma and lead to secondary damage years later and can also be caused intrinsic cord tumours

Question 18

What is the pathophysiology of Syringomyelia?

Answer 18

• Expanding cavity in cord gradually destroy spinothalamic neurone, anterior horn cells and lateral corticospinal tracts. In medulla, lower cranial nerve nuclei are affected
• Progressive over several decade. Sudden deterioration sometimes follow minor trauma or occurs spontaneously

Question 19

What are symptoms and signs of Syringomyelia?

Answer 19

• Upper limb pain exacerbated by exertion or coughing is typical
• Paraparesis
• Preserved light touch, vibration and proprioception (unless it progresses to affect dorsal column pathways too)
• The classical presentation of a syrinx is a patient who has a ‘cape-like’ (neck and arms) loss of sensation to temperature but preservation of light touch, proprioception and vibration.
• Spastic weakness (predominantly of the upper limbs)
• Paraesthesia
• Neuropathic pain
• Upgoing plantars and bowel and bladder dysfunction.
• Scoliosis will occur over a matter of years if the syrinx is not treated. It may cause a Horner’s syndrome due to compression of the sympathetic chain, but this is rare.

Question 20

What are signs of substantial cervical syrinx?

Answer 20

• Suspended area of dissociated sensory loss
• Loss of upper limb reflexes
• Muscle wasting in hand and forearm
• Spastic paraparesis
• Brainstem signs – syrinx extends into brainstem and may be tongue atrophy and fasciculation, bulbar palsy, Horner’s syndrome and impairment of facial sensation

Question 21

What is the investigations for syringomyelia?

Answer 21

• Full spine MRI with contrast – Demonstrate cavity and herniation of cerebellar tonsils
• Brain MRI to exclude Chiari malformations

Question 22

What is the management for Syringeomyelia?

Answer 22

• Surgical decompression of foramen magnum often causes syrinx to collapse
• Treat the cause

Question 23

What is Becker Muscular Dystrophy?

Answer 23

• Becker muscular dystrophy there is a non-frameshift insertion in the dystrophin gene resulting in both binding sites being preserved leading to a milder form
• Develops after the age of 10 years
• Intellectual impairment much less common