Neuro Flashcards
Define Huntington’s
• Autosomal dominant trinucleotide repeat disease (CAG repeat on chr4) characterised by progressive chorea and dementia, typically commencing in middle age
Aetiology Huntington’s
- Expanded CAG repeat at N-terminus of gene that codes for huntingtin protein
- Results in toxic gain of function causes atrophy and neuronal loss of striatum and cortex
- Autosomal dominant earlier age of onset with each successive generation
• Early mild symptoms o Lability o Dysphoria (a state of unease or generalised dissatisfaction with life) o Irritability o Incoordination o Fidgeting o Clumsiness o Mental inflexibility o Anxiety o Develops into dementia
• Later stages o Rigid o Involuntary, jerky, dyskinetic movements often accompanied by grunting and dysarthria – CHOREA o Dementia o Fits o Akinetic o Bed-bound o Death
Huntington’s
Investigations Huntington’s
• Diagnosis is often clinical
• Genetic Analysis
o Diagnostic if there are > 39 CAG repeats in the HD gene
o Reduced penetrance leads to an intermediate number of CAG repeats
• Imaging
o Brain MRI or CT may show symmetrical atrophy of the striatum and butterfly dilation of the lateral ventricles
Define Myasthenia gravis
• Chronic autoimmune disorder of post-synaptic membrane of NMJ in skeletal muscle producing weakness.
Aetiology Myasthenia gravis
• Antibodies against nicotinic acetylcholine receptor which interferes with neuromuscular transmission via depletion of post-synaptic receptor sites
• Lambert-Eaton Syndrome – paraneoplastic subtype of MG caused by autoantibodies against pre-synaptic calcium channels, leading to impairment of ACh release
o Can be paraneoplastic (small cell lung cancer) or autoimmune
• MG is associated with other AI conditions (eg. pernicious anaemia)
• Muscle weakness that worsens with repetitive use/end of day – fatigability
o Order of muscle weakness: extraocular bulbar face neck limb girdle trunk
• Occular symptoms
o Dropping eyelids
o Diplopia (double vision)
• Bulbar symptoms
o Facial paresis (myasthenic snarl)
o Dysarthria (speech disorder)
o Dysphagia (difficulty swallowing)
- Proximal limb weakness
- Shortness of breath
Myasthenia gravis
Investigations Myasthenia gravis
• Serum acetylcholine receptor antibody analysis
o Result above a certain point for given assay
• Muscle specific tyrosine kinase antibodies
o Positive in 70% of generalised MG
• Serial pulmonary function tests
o Low FVC and NIF (negative inspiratory force)
Define Meningitis
• Inflammation of the leptomeningeal (pia and arachnoid mater) coverings of the brain, most commonly due to infection
• Immune response to infection causes cerebral oedema raising ICP, causing 2 effects:
o Herniation
o Raised ICP + systemic hypotension ↓ cerebral perfusion
Aetiology Meningitis
• Bacterial o Neonates ♣ Group B streptococci ♣ E. coli ♣ Listeria monocytogenes
o Children
♣ Haemophilus influenza
♣ Nseisseria meningitides
♣ Streptococcus pneumoniae
o Adults
♣ Neisseria meningitides
♣ Streptococcus pneumoniae
♣ Tuberculosis
o Elderly
♣ Streptococcus pneumoniae
♣ Listeria monocytogenes
• Viral o Human enteroviruses o HSV 1 & 2 o Mumps o VZV o HIV
• Fungal o Cryptococcus (common cause of meningitis in HIV patients)
• Others
o Aseptic meningitis (not due to microbes)
o Mollaret’s meningitis (recurrent benign lymphocytic meningitis)
• RISK FACTORS o Close communities (e.g. college halls) o For bacterial: being under 5 or over 60 yrs o Male o Immunosuppressed o Basal skull fractures o Mastoiditis o Sinusitis o Inner ear infections o Alcoholism o Immunodeficiency
o Severe headache o Leg pain o Cold hands and feet o Abnormal skin o Neck stiffness o Photophobia o Fever o Irritability/altered mental state o ↓ consciousness o Vomitting
o Photophobia o Neck stiffness o Kernig's Sign o Brudzinski's Sign o Pyrexia o Tachycardia o Hypotension o Skin rash o Altered mental state
Meningitis
Investigations meningitis
• Bloods
o U&Es, FBC (low WCC = immunocompromised – needs help), LFT, glucose, coagulation screen
o Two sets of blood cultures (as well as throat swabs, rectal swabs)
• Imaging
o CT scan - exclude mass lesion or raised ICP before LP
o Other contraindications for LP: suspected intracranial mass lesion, focal signs, papilloedema, trauma, middle ear pathology, major coagulopathy
• Lumbar Puncture – usually done after CT but if GCS 15, no symptoms of raised ICP and no focal neurology: can be done without CT to save time. o Measure opening pressure – 7-18cm CSF is normal, in meningitis may be >40 o Send CSF for MC&S, Gram stain, protein, glucose, virology and lactate o Bacterial meningitis: ♣ Cloudy CSF ♣ High neutrophils ♣ High protein ♣ Low glucose o Viral (‘aseptic’) meningitis – for this, also do CSF PCR ♣ Clear CSF ♣ High lymphocytes ♣ High protein ♣ Normal glucose o TB meningitis: ♣ Fibrinous CSF ♣ High lymphocytes ♣ High protein ♣ Low glucose
Management meningitis
• IMMEDIATE IV Antibiotics (before LP)
o First choice: 3rd generation cephalosporin (e.g. cefotaxime or ceftriaxone)
o If >55 yrs, add ampicillin too (for Listeria)
o Blind: GIVE IM BENZYLPENICILLIN IF IN GP. If allergic to this: ceftriaxone
• Dexamethasone IV
o Given shortly before or with the first dose of antibiotics
o Associated with a reduced risk of complications
• Then, if no signs of high ICP: do LP
• Resuscitation
o Manage in ITU
o Notify public health services
Complications meningitis
- Septicaemia
- Shock
- DIC
- Renal failure
- Seizures
- Peripheral gangrene
- Cerebral oedema
- Cranial nerve lesions
- Cerebral venous thrombosis
- Hydrocephalus
- Waterhouse-Friderichsen Syndrome (bilateral adrenal haemorrhage caused by severe meningococcal infection)
Raised ICP
- ↑ in volume of contents inside the cranium
- Can be mass effect, oedema or obstruction to fluid outflow
- Normal ICP in adults is <15mmHg
Aetiology raised ICP
- Primary or metastatic tumours
- Head injury
- Haemorrhage
- Infection – meningitis, encephalitis, brain abscess
- Hydrocephalus
- Cerebral oedema
- Status epilepticus
• Headache: worse on coughing and leaning forwards, worse in morning
• Vomiting
• Altered GCS – drowsiness, irritability, coma
• History of trauma
Poor vision
- Altered GCS
- Falling pulse and rising BP (Cushing’s response)
- Cheyne-Stokes respiration – progressively deeper and sometimes faster breathing followed by a gradual decrease that results in a temporary stop in breathing - cycle repeats
- Pupil changes – constriction first, later dilatation
- Reduced visual acuity
- Peripheral visual field loss
- Papilloedema – unreliable sign but venous pulsation at the disc may be absent
Raised ICP
Investigations raised ICP
- U&E, FBC, LFT, glucose, serum osmolality, clotting, blood culture
- Consider toxicology screen
- CXR – any source of infection may lead to abscess
- CT head
- Consider LP if safe – measure opening pressure
Define Horner’s
• Condition resulting from disruption of sympathetic nerves supplying the face resulting in triad of:
o Partial Ptosis – eye lid drooping
o Miosis – pupillary constriction
o Anhydrosis – ipsilateral loss of sweating
o (and enopthalmos – sunken eye)
Aetiology Horner’s
• Caused by disruption of sympathetic fibres
• Causes – disruption to nerves can be @ different locations:
o Brainstem: demyelination, vascular disease, stroke
o Cord: syringomyelia
o Thoracic outlet: Pancoast’s tumour (apical lung tumour)
o On the sympathetic’s trip on the internal carotid artery into the skull (carotid artery dissection)
o At the orbit
- Inability to open eye fully on affected side
- Loss of sweating
- Facial flushing
- Orbital pain/headache
• Ptosis
• Miosis
• Anhydrosis
Enopthalmos
Horner’s
Investigations Horner’s
• Investigations are directed towards figuring out the underlying cause • CXR - apical lung tumour • CT/MRI - cerebrovascular accidents • CT angiography - dissection
Management Horner’s
- Horner’s syndrome is a sign not a disease in itself
- So, the management depends on the cause (e.g. management for carotid dissection is very different to management of apical lung tumours)
