Infections Of The Nervous System

Question 1

What is cerebrospinal fluid (CSF)?

Answer 1

Substance similar to blood plasma with less proteins and few cells produced by choroid plexus in brain ventricles, circulating through the sub-arachnoid space around the brain and spinal cord providing impact protection and metabolic support to the CNS

Question 2

What is intra-cranial pressure (ICP)?

Answer 2

Pressure inside the skull most easily measured in sub-arachnoid space around the lumbar spine where the spinal cord ends via a lumbar puncture and subsequent measure of opening pressure with an attached manometer (accurate enough if no blockages in CSF circulation e.g. hydrocephalus)

Question 3

What is the difference between meningitis and encephalitis?

Answer 3

Meningitis is inflammation (usually infectious) of the meninges whereas encephalitis is inflammation (usually infectious) of the brain but clinical features overlap - can also get meningoencephalitis (inflammation of meninges and brain)

Question 4

What is myelitis?

Answer 4

Inflammation (sometimes infectious) of the spinal cord

Question 5

What different types of abscess exist in the brain?

Answer 5

Cerebral = in the brain

Epidural = epidural space in area where a epidural puncture has been done

Subdural = subdural space in area where lumbar puncture has been done

Question 6

What is an abscess?

Answer 6

Collection of pus

Question 7

What are the causes of bacterial meningitis?

Answer 7

Neisseria meningitidis (meningococcus)
Streptococcus pneumoniae (pneumococcus)
Group B Streptococci 
Haemophilus influenzae type B (HiB)
Listeria monocytogenes 
Mycobacterium tuberculosis

Question 8

What are the viral and fungal causes of meningitis?

Answer 8

Viral: enterovirus, VZV, HIV, mumps and measles (younger people)

Fungal: Cryptococcus neoformans

Question 9

What are the causes of encephalitis?

Answer 9

Viral: HSV (cold sores), VZV, HIV, arboviruses and rabies

Question 10

What are the causes of cerebritis?

Answer 10

Bacterial: associated with immunodeficiency or abscesses

Question 11

What are the causes of abscess?

Answer 11

Bacterial: mostly Streptococci (Pneumoniae most commonly or upper airway/sinus infections)

Question 12

What are the causes of cysts?

Answer 12

Parasitic: toxoplasmosis, cysticercosis and echinococcosis (hydatid)

Question 13

What are the causes of myelitis?

Answer 13

Viral: poliomyelitis and rabies

Question 14

What types of meningitis are currently most common?

Answer 14

Vaccinations against all types of N. Meningitidis and H. Influenzae B so all of these are practically non-existent now so other strains becoming more predominant e.g. viral

Question 15

Who are the most common individuals to get meningitis?

Answer 15

Infants < 1yr
Younger children
Later teenagers-early 20s (new university students)
Individuals living in the meningitis belt in Africa
Individuals on The Hajj pilgrimage (must get vaccine prior to this now)

Question 16

Why are university students more prone to meningitis?

Answer 16

Most people naturally carry the germ in the back of their throat causing no problems for them or anyone else but when people start to mix, if they have not been exposed to it before they may become infected

Question 17

What overlapping clinical syndromes can meningococcal infections cause?

Answer 17

Meningitis on its own (restricted to meninges), septicaemia on its own (all over body but not in meninges) and commonly meningitis and septicaemia together

Question 18

What are the features of CNS infection?

Answer 18

Focal CNS signs
Fever
Reduced GCS

More common in meningitis:
Headache 
Neckstiffness
Photophobia
Purpuric rash (ONLY meningococcal meningitis/septicaemia)

More common in encephalitis:
Confusion
Seizures

Question 19

What is the best motor response scale of the GCS?

Answer 19

6 - obeys commands
5 - localising response to pain
4 - withdraws from pain
3 - flexor (decorticate) response
2 - extensor (decerebrate) response)
1 - no response

Question 20

What is the best verbal response scale of the GCS?

Answer 20

5 - normal speech
4 - confused speech
3 - inappropriate speech (words only)
2 - incomprehensible (sounds only)
1 - no response

Question 21

What is the best eye response scale of the GCS?

Answer 21

4 - eyes open spontaneously
3 - eyes open to voice
2 - eyes open to pain
1 - no response

Question 22

What symptoms are usually sufficient to make a diagnosis of bacterial meningitis?

Answer 22

Any 2 of:
Headache
Neck stiffness
Fever > 38 
GCS < 14

Question 23

Who is most likely to get meningococcal meningitis?

Answer 23

Children and young adults with possible acute outbreaks, sepsis, purpuric rash (beginning of skin gangrene) and peripheral gangrene

Question 24

Who is most likely to get pneumococcal meningitis?

Answer 24

Associated with RTI, trauma, immunocompromised and elderly individuals with less acute outbreaks (building up over days), no rash, high mortality and morbidity

Question 25

Who is most likely to get Group B Streptococcus meningitis?

Answer 25

Neonates acquire the bacteria during birth as the mother may carry it - low morality but still risk of CNS damage

Question 26

Who is most likely to get Listeriosis meningitis?

Answer 26

Neonates, elderly, immunocompromised and pregnant individuals - meningoencephalitis, rhomboencephalitis with blood cultures +ve

Question 27

How does Tuberculosis meningitis typically present?

Answer 27

Insidious onset of fever, confusion, coma, high CSF protein (~8ml required for culture)

Question 28

Who is most likely to get brain abscess meningitis?

Answer 28

Associated with chronic URTIs e.g. sinusitis and otitis, immunocompromised or individuals with learning disabilities (not good at expressing whats wrong with them) with insidious onset or seizure presentation

Question 29

What investigations should you consider in a patient with head injury?

Answer 29

FBCs & inflammatory markers (e.g. CRP) Renal function (U+Es) Coagulation tests (APTT/PT) Consider CT head if risk of raised ICP or brain lesions LP CSP opening pressure/appearance Additional tests for M. Tuberculosis and Cryptococcus

Question 30

What do you want to test for in a lumbar puncture when the patient has head injury?

Answer 30

Sample 1 + 3 sent for microscopy/microbiology - RCC/WCC and differential, organisms and PCR tests (if you've punctured a vessel, 1 will have a lot of RBCs but 3 will have less whereas consistent blood indicates a problem) Sample 2 sent for biochemistry - protein/glucose with blood glucose to compare

Question 31

Why do you want to test renal function in head injury patients?

Answer 31

Kidney function can be damaged during sepsis

Question 32

Why do you need to do a coagulation test in head injury patients?

Answer 32

Make sure patient has normal clotting before performing a lumbar puncture

Question 33

What is there a risk of when doing a lumbar puncture in patients with raised intracranial pressure (ICP)?

Answer 33

Coning - brain herniating through the foramen magnum crushing the base of the brain = life-threatening consequences - why you do a CT head before doing a lumbar puncture if there are indications of raised ICP (otherwise don't bother)

Question 34

Why do you do 2 sets of blood cultures in head injury patients?

Answer 34

To avoid contamination when time is of such essence

Question 35

What will you see in a CT if there is raised intracranial pressure (ICP)?

Answer 35

Midline shift | Loss of sulci and ventricles

Question 36

Where do you do a lumbar puncture?

Answer 36

Above spinous process of L4 roughly

Question 37

What layers will you go through when performing a lumbar puncture?

Answer 37

``` Skin Subcutaneous tissue Supraspinous ligament Interspinal ligament Ligamentum flavum Epidural space (contains internal vertebral venous plexus) Dura Arachnoid Subarachnoid space ```

Question 38

What should cerebrospinal fluid (CSF) look like?

Answer 38

Clear and colourless with a tinge of yellow

Question 39

What might a patient with meningitis cerebrospinal fluid (CSF) look like?

Answer 39

Turbid cloudy appearance due to bacteria however this is not seen so much now as patients present earlier

Question 40

What cerebrospinal fluid (CSF) results are abnormal?

Answer 40

Opening pressure > 18cm of water using manometer RCC > 1 per mm^3 (either traumatic LP or SAH so compare bottles 1 and 3) WCC > 5 per mm^3 Protein > 1g/L and glucose < 50% of blood glucose

Question 41

What will the cerebrospinal fluid (CSF) show in a bacterial infection?

Answer 41

High WCC > 5 per mm^3 mostly neutrophils High protein > 1g/L Low glucose < 50% of blood glucose

Question 42

What will the cerebrospinal fluid (CSF) show in a viral infection?

Answer 42

Slightly high WCC > 5 per mm^3 mostly lymphocytes Slightly high proteins > 1g/L Normal glucose in comparison to blood glucose

Question 43

What will the cerebrospinal fluid (CSF) show in tuberculosis infection?

Answer 43

High WCC > 5 per mm^3 mostly lymphocytes Very high protein > 1g/L Low glucose < 50% of blood glucose

Question 44

What type of White Blood Cell (WBC) will be high if there is an abscess?

Answer 44

Lymphocytes

Question 45

How do you manage a CNS infection?

Answer 45

1. Supportive treatment and Sepsis | 2. Find right antibiotic for cause

Question 46

How do you treat bacterial meningitis?

Answer 46

Ceftriaxone, Cefotaxime or Benzylpenicillin (penetrate BBB well)for 1 week with Dexamethasone IV QDS for 4 days If severe Penicillin allergy give Vancomycin, Meropenem, Rifampicin or Cotrimoxazole

Question 47

How do you treat listeriosis?

Answer 47

Amoxicillin IV QDS for 3 weeks

Question 48

How do you treat viral encephalitis?

Answer 48

Aciclovir IVTDS for 3 weeks

Question 49

How do you treat tuberculosis?

Answer 49

Rifampicin, Isoniazid, Pyrazinamide, Ethambutol and Dexamethasone IV QDS for 1 week converted to

Question 50

Why is Dexamethasone given in CNS infections?

Answer 50

If infection is severe, there may be cranial nerve compression injuries which may induce permanent damage if not dealt with by this steroid - benefit small but in certain cases its recommended

Question 51

What is the prognosis of meningococcal meningitis (w/o septicaemia)?

Answer 51

Mortality ~10% CN palsies e.g. deafness and squints Post-infective immunological complications e.g. arthritis and pericarditis

Question 52

What is the prognosis of meningococcal septicaemia (sepsis with or w/o meningitis)?

Answer 52

Mortality ~40% (higher as patients present later due atypical signs unlike meningitis) Gangrene of purpura and peripheries - produces ulcers that could cause patient to lose limbs or heal if caught early Post-infective immunological complications e.g. arthritis and pericarditis

Question 53

What is the prognosis of pneumococcal meningitis?

Answer 53

Mortality ~25% CN palsies e.g. deafness Relapses (even after a week of treatment) and metastatic infections

Question 54

What chemoprophylaxis can be used for meningococcus infection?

Answer 54

For household and kissing contacts - Ciprofloxacin single dose and Rifampicin BD for 2 days Not required for patient is treated with Ceftriaxone

Question 55

What immunoprophylaxis can be used for meningitis?

Answer 55

Vaccines against: - Meningococcus A, C, W135, Y and now B - Pneumococcus (7 serotypes) - Haemophilus Influenzae type B (HiB) - Some viral causes of meningitis