Nerve conduction studies

Polymyositis - reduced amplitude and duration of motor units
Motor neurone disease - fibrillation due to denervation
Myasthenia gravis - diminished response to repetitive stimulation
Lambert Eaton syndrome - enhanced response to repeated stimulation
Myotonia dystrophia - high frequency action potentials (Kamikazee discharge)
Demyelinating neuropathy - slow nerve conduction velocity
Axonal neuropathy - diminished action potential

Cluster headache

- a.k.a migrainous neuralgia
- caused by superficial temporal artery smooth muscle hyperperactivity to 5HT
- commoner in male
- rapid onset severe pain around one eye which may become watery and bloodshot with lid swelling, lacrimation, facial flushing, rhinorrhoea, and occasionally transient Horner syndrome
- unilateral, lasts 15-160mins, often nocturnal (waking sufferers at onset of REM sleep)
- treatment: acute attack (100% oxygen at 10-12L/min for 15mins and s/c sumatriptan 6mg or nasal spray sumatriptan 20mg) , prophylaxis (verapamil 120-160mg tds, topiramate)

Guillain Barre syndrome

- a.k.a acute autoimmune inflammatory demyelinating polyneuropathy
- segmental demyelination
- 1-2/100,000/year
- bimodal distribution with peak age 15-35 and 50-75 years
- symmetrical ascending muscle weakness preceded by diarrhea (eg:campylobacter) and chest infection (eg: mycoplasma).
- maximal weakness occurs 2 weeks after initial onset of symptom, weakness almost always symmetrical
- other triggers: HIV,EBV, vaccinations, zoster
- associated with autonomic dysfunction (sweating, tachycardia, BP changes, arrhythmias) and hyporeflexia
- monitor force vital capacity (FVC)
- nerve conduction studies: slow conduction
- CSF: albuminocytological dissociation (raised protein, normal cell count)
- GBS is associated with anti-ganglioside GM1 antibody
- Miller-Fisher variant is associated with anti-G1q antibody
- treatment: IVIG, plasmapheresis
- mortality about 10%

Trypanosomiasis

American trypanosomiasis (Chagas' disease)
- caused by T.cruzi
- spread by reduviids (triatomine bugs)
- erythematous indurated nodule (chagoma) at side of infection which may then scar
- fever, myalgia, rash, lymphadenopathy, hepatosplenomegaly, unilateral conjunctivitis, periorbital edema (Romana's sign), myocarditis, meningoencephalitis
- trypomastigotes seen or grown from blood in acute disease, serology in chronic disease
- treatment: nifurtimox, benznidazole

 

African trypanosomiasis (sleeping sickness)
- T.gambiense (slow, wasting illness), T.rhodesiense (rapidly progressive illness)
- spready by tsetse flies
- tender subcutaneous nodule (chancre) at site of infection
- 2 stages
  i) haemolymphatic
     - fever, rash, rigors, headache, hepatosplenomegaly, lymphadenopathy
     - Winterbottom's sign (posterior cervical node enlargement)
  ii) meningoencephalitic
     - convulsion, agitation, confusion,apathy, depression, ataxia, dementia, hypersomnolence, coma
- treatment: suramin, melarsoprol

 

Basic statistic (4)

Paired student t test 
 - compare 2 paired groups of patients with parametric data (normal distribution)
Wilcoxon test
 - compare 2 paired groups of patients with non parametric data (skewed distribution)


Unpaired student t test
 - compared 2 unpaired groups of patients with parametric data (normal distribution)
Mann-Whitney U test
 - compared 2 unpaired groups of patients with non parametric date (skewed distribution)

Chi-squared test
 - to compare percentages or proportions of categorical data (2 X 2 contingency table)

Huntington's disease

- autosomal dominant (full penetrance)
- prevalence: 5:100,000
- a trinucleotide repeat disorder (CAG repeat)
- chromosome 4
- marked loss of neurones in the caudate nucleus and putamen
- increase in protein Huntingtin (polyglutamine)
- dementia, ataxia, abnormal choreiform movements, ophthalmoplegia
- diagnosis by DNA analysis
- treatment: phenothiazine for symptomatic control

Motor neuron disease

- cluster of major degenerative disease characterised by selective loss of neurons in motor cortex, cranial nerve nuclei, and anterior horn cells
- 4 clinical patterns:
   i) amyotrophic lateral sclerosis
   ii) progressive bulbar palsy
   iii) progressive muscular atrophy - anterior horn cell lesion
   iv) primary lateral sclerosis - mainly UMN sign (loss of Betz cell in motor cortex)
- onset more than 50 years of age, with incidence increasing with advancing age
- men affected more frequently
- 5-10% familial (mutation chromosome 21, SOD 1 gene)
- mixed lower motor neuron and upper motor neuron signs
- No sensory loss or sphincter disturbance and never affects eye movement
- 75% presents with limb symptoms, 25% presents with bulbar symptoms (poor prognosis)
- EMG: fasciculation and fibrillation potentials in upper and lower limbs
- El Escorial criteria for ALS (shown below)
- treatment: Riluzole (antiglutamate)

Facioscapulohumeral dystrophy (FSHD)

- autosomal dominant (gene locus 4q35)
- onset 12-14 years old
- initial weakness is seen in facial muscles, starting in orbicularis oculi, orbicularis oris and zygomaticus
- shoulder weakness is common presenting symptom
- signs: weakness of face ('ironed out' expression), winging of scapulae
- life expectancy is normal but up to 15% patients are severely disabled and wheelchair bound

Foster Kennedy syndrome

- frontal lobe tumor (commonly meningioma in sphenoidal wings)
- causing ipsilateral disc atrophy (compression) + contralateral disc swelling (increased ICP)

Idiopathic intracranial hypertension

- a.k.a benign intracranial hypertension or pseudotumor cerebri
- most common in obese young women between age 20-50
- headache (worse with straining and bending forward), visual blurring with papilloedema are common features
- 4 diagnostic criteria must be met
  i) sign and symptoms of increased ICP
  ii) normal or small size ventricles seen on neuroimaging
  iii) increased CSF pressure with normal composition
  iv) papilledema
- associated factors: OCP, steroids, vitamin A, tetracycline, nitrofurantoin
- opening pressure on LP : >25cm water
- complication: optic nerve infarction or blindness
- treatment: repeated lumbar puncture, acetazolamide, thiazide diuretics, surgical decompression or shunting (lumboperitoneal shunt), trial of steroid for severe cases at risk of visual impairment due to papilloedema, optic nerve fenestration