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Diagnosis and investigations of conditions of the: > CNS > Flashcards

CNS Flashcards

1
Q

When doing a lumbar puncture, what information do we gather?

A
  1. CSF pressure (indicates pressure on brain)
  2. Fluid colour (infection, haemolysis, bleeds)
  3. Fluid contents (WCCs/proteins present)
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2
Q

Where do we insert our needle during a lumbar puncture?

A

Equidistant between the iliac crests.

Between L3-4 or L4-5 (lumbar cistern: subarachnoid spaceL2-S2)

(Since spinal cord finishes at L2)

  • we go through deep muscle > ligaments > dura (pop!)
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3
Q

What is a normal intracranial pressure? (In mmhg)

A

<15 mmhg

It is normal for it to be low, this means the brain stem isn’t pushed down the foremen magnum.
It can even become negative when standing

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4
Q

What is a raised intracranial pressure? (In mmhg)

A

> 20 mmhg

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5
Q

What is the monroe-Kelly doctrine?

Think of raised intracranial pressure

A

The skull is a fixed volume, so it’s compliance decides the intracranial pressure

Compliance = Increase in one component of the skull contents displaces another component(brain, CSF, blood)

Three phases of increased intracranial volume exist:

  1. High compliance = blood and CSF exit the skull so ICP doesn’t increase as intracranial volume increases
  2. Compliance lowers = no more blood or CSF to remove, ICP starts to rise as intracranial volume increases
  3. No compliance = as intracranial volume increases the ICP rises very rapidly
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6
Q

Which infections occur with a clear CSF?

A

Fungal and viral

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7
Q

Which infections cause the CSF to be turbid (cloudy)?

A

Bacterial and TB infections

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8
Q

Which infections cause CSF to become viscous?

A

Fungal and TB

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9
Q

In bacterial meningitis, which will be increased: polymorphs or lymphocytes?

A

Bacterial = increased polymorphs

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10
Q

In viral meningitis, which will be increased: polymorphs or lymphocytes?

A

Viral = lymphocytes increased

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11
Q

In fungal meningitis or TB, which will be increased: polymorphs or lymphocytes?

A

Fungal and TB = increased polymorphs AND increased lymphocytes

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12
Q

In bacterial meningitis, how will the glucose and protein levels be in CSF?

A

Bacterial:

Very low glucose

High protein

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13
Q

In viral meningitis, how will the glucose and protein levels be in CSF?

A

Viral:

Glucose is normal (no consumption)

Protein is raised

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14
Q

In TB and fungal meningitis, how will the CSF protein and glucose be affected?

A

TB and fungal:

Glucose is low

Protein is very high

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15
Q

A patient presents with a headache:

What extra finding or circumstance would indicate for neuroimaging?

Basically the associated red flags.

(Examination, natural history, high risk groups)

A
  • Focal neurological signs (On examination e.g. visual change, muscle weakness)
  • A change in headache semiology (A change in the pattern and severity of longstanding headaches)
  • Nocturnal headaches (Worsening headaches which are waking the patient at night)
  • New onset headache in the middle aged .
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16
Q

A patient presents with unilateral headache and temporary loss of vision in the same sided eye:

What is your first test?

A

ESR and CRP

This is giant cell arteritis presentation, a medical emergency.

17
Q

How do you confirm your diagnosis of giant cell arteritis? (AKA temporal arteritis)

A

Temporal artery biopsy in multiple places

18
Q

What is the first line investigation for suspected subarachnoid haemorrhage?

A

CT head

19
Q

What does the glass test indicate for? And why is it relevant to meningitis investigations?

A

If a clear glass tumbler placed in a rash does not make the rash disappear under pressure, it indicates septicaemia

Sepsis is a contraindication for lumbar puncture

20
Q

Which signs are contraindications for lumbar punctures?

A

New onset rash (Sepsis)

Thrombocytopenia (can’t clot puncture site)

Signs of infection (fever, inflammation - sepsis risk)

Papilloedema (raised ICP means depressurisation can pull brain stem downwards - resp depression)

Focal neurological signs (indicate SOL and raised ICP)

Overall:

  1. Signs of raised ICP
  2. Coagulation defects
  3. Signs of infection near puncture site
21
Q

What are the signs of a brain tumour on MRI?

A

The tumour itself may be visible.

Local swelling around the tumour.

Guru and sulci are lost: outer border of affected hemisphere is smooth (roughenings are gyru and sulci)

22
Q

What are the signs specific to a space occupying lesion in the occipital lobe?

A

Visual field loss: hemianopia, loss of vision to one/both eyes

23
Q

What are the signs specific to a space occupying lesion in the parietal lobe?

A

Sensory symptoms: anosmia, touch, recognition.

Aphasia and coordination difficulties.

Visual field defects.

24
Q

What are the signs specific to a space occupying lesion in the temporal lobe?

A

Dysphasia

Visual field defects (adjacent to optic nerve route)

25
Q

What are the signs specific to a space occupying lesion in the cerebellum?

A

Cranial nerve palsies

Tremors

Nystagmus

Dysmetria (lack of coordination of movement, causes overshooting and undershooting)

Ataxic gait

26
Q

What are the signs specific to a space occupying lesion in the frontal lobe?

A

Personality change

Dementia

Dysphasia

Muscle weakness

27
Q

How many 30+ minute headaches do you need per month to be diagnosed with chronic tension headache?

A

> 15 headaches per month for more than three months

28
Q

How do we diagnose cause of transient loss of consciousness?

A

Most of the diagnosis is down to the history; it can present significant opportunity to be incorrectly diagnosed.

In short: Diagnosis of exclusion
Uncomplicated vasovagal syncope
Situational syncope
Orthostatic hypotension
Epilepsy
Cardiogenic
1. History from the patient
Presyncopal symptoms (light headedness, dizziness, visual blurring, ringing in ears, auditory distortion, sweating, feeling cold)
Seizure symptoms (Pre-seizure: epigastric rising sensation, abnormal taste/smells, dejavu.)
(Post-seizure: where were they after, confusion, recognise people around them)
2. History from witnesses:
What they were doing
Posture before event
Any warning symptoms
Colour change
Pale/red in the face
Movement in the limbs; stiffness, jerking or twitching
How long did movements continue for
Tongue biting (which side)
Injury during the event
Duration of event
How long after movement stops did patient come around
Weakness down one side during recovery
Confusion present/absent
3. Past history:
Previous episodes, number and frequency
Medical history
Family history of cardiac disease
Current medications
  1. Vital signs, neurological and cardiovascular examinations
  2. 12 lead ECG, look for red flags:
    - heart blocks
    - evidence of long or short QT intervals
    - ST segment abnormalities
    - T wave abnormalities
    - Persistent Bradycardia
    - L/RVH
    - Atrial arrhythmias
    - Heart murmur
    - New/unexplained dyspnoea
    - Family history of sudden cardiac death under 40
  3. If red flags found: urgent referral to cardiology
    - If NO red flags found:
  4. Diagnose uncomplicated vasovagal syncope (AKA faint) if:
    No features of alternative diagnosis
    Features are PPP ;
    -posture is prolonged standing/prevented by lying
    -provoked by pain or medical procedure
    -prodromal symptoms (sweating, feeling warm before)
  5. Diagnose situational syncope if:
    No features of alternative diagnosis
    Syncope is consistency provoked by straining during micturition, coughing or swallowing
    = micturition syncope, cough syncope or swallow syncope
  6. Diagnose Orthostatic hypotension if:
    No features of situational/uncomplicated syncope
    Provocation is caused by changing from lying/sitting to standing
    Measure sitting and standing BP to confirm.
  7. Suspect epilepsy when they have 1 or more feature:
    Bitten tongue
    Head turning to one side during TLOC
    No abnormal behaviour beforehand
    Unusual posturing
    Prolonged limb jerking (short jerking can occur in faints)
    Confusion after the event
    Prodromal deja vu
    -Refer for specialist assessment within 2 weeks-
Features making it less likely:
Prodromal symptoms abolished by sitting/lying
Sweating before episode
Prolonged standing precipitating TLOC
Pallor during the episode
  1. Investigate for cardiogenic syncope, Epilepsy and orthostatic hypotension not suspected:
    Refer for specialist cardiovascular assessment
    Repeat ECG and investigate for arrythmias, structural heart disease, neurogenic (vasovagal and carotid sinus) syncope
29
Q

How do we diagnose epilepsy?

A
  1. Screen in A+E based on history:
    Abnormal movements predominates
    Disturbed awareness, thoughts and sensations predominate
    -These two categories have subcategories that narrow the list of possible differentials-
  2. Refer to specialist for epilepsy
  3. Diagnosis is not made based on the presence/absence of single features
    If any uncertainty exists, referral to a cardiogist is to be considered
  4. EEG performed to support diagnosis of epilepsy
    Helps determine seizure type and epilepsy syndrome (based on age of onset, seizure type, EEG characteristics and other features)
  5. Neuropsychological assessment: in cases of learning disabilities or cognitive dysfunction
  6. Neuroimaging by MRI: Identify any abnormalities that may be causing epilepsy, potentially supported with blood tests
    - Final product is 1) seizure type 2) epilepsy syndrome, and 3) aetiology
30
Q

What are the recommendations for a patient attending a first seizure clinic?

A
  1. Don’t drive
  2. Bring someone who witnessed the seizure

They are not normally given anti epileptic medication unless condition causing epilepsy makes another seizure very likely - e.g. brain tumours

31
Q

In a patient with reduced GCS after a seizure, what should be the first investigation?

A

Blood glucose

Anyone with altered conscious level must be suspected of hypoglycaemia.

Hypoglycaemia could also be the cause of the seizure.

32
Q

In the case of a post-operative surgical patient who has a seizure (and no history of seizures) what should be the first investigation?

A

Serum electrolytes - hyponatremia and hypernatremia can both cause seizures

In the post-operative stage, patients receive IV fluids, these can contain insufficient or excess sodium, thereby inducing seizure.

33
Q

How is a seizure defined as general or focal?

A

If it starts on one side it is focal, regardless of any ensuing progression to bilateral.

34
Q

What features should we expect from a non-epileptic attack disorder?

A

Gradual onset
Prolonged duration
Abrupt termination
Accompanied by: closed eyes, rapid breathing, fluctuating motor activity, and episodes of motionless unresponsiveness.

CNS exam, CT, MRI, and EEG are normal.

It may coexist with true epilepsy

35
Q

How do you diagnose encephalitis?

A

FBC
Cultures and CSF sampling
CT

Diagnosis and investigations of conditions of the: (18 decks)

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