Neuro Flashcards
UMN vs LMN lesion features
LMN shows PERIPHERAL NS symptoms:
muscle wasting, fasciculations, reduced tendon reflexes and tone,
forehead involved if CN VII involved in lesion,
signs are on the same side as the lesion, hypotonia,
FOCAL pattern of weakness (only specific muscles innervated by nerve)
UMN shows CENTRAL NS symptoms:
increased tone and reflexes, upgoing plantars (Babinski +ve),
if facial weakness then forehead is spared,
signs are on OPPOSITE side of lesion,
No muscle wasting,
Extensor planter response present
PYRAMIDAL pattern of weakness seen: extensor muscles affected but flexors are not etc. eg in STROKE
UMNs mainly form sensory and intermediate neurons with inhibitory effect on LMNs reflexes, therefore damage to an UMN or its connections with LMN will EXAGGERATE the reflexes
ACh, function and examples of malfunction
Noradrenaline function and examples of malfunction
ACh:
Enables muscle action, learning and memory
In Alzheimer’s, ACh producing neurons deteriorate
NA:
Helps control alertness and arousal
Undersupply is linked to depressed mood
Dopamine functions, examples of malfunctions
Influences movement, learning, attention and emotion
Excess dopamine receptor activity is linked to schizophrenia
Starved of dopamine, the brain produces the tremors and decreased mobility of Parkinson’s
Serotonin (5HT) function and examples of malfunction
Affects mood, hunger, sleep and arousal
Undersupply is linked to depression
GABA and glutamate function and examples of malfunction
GABA:
Major inhibitory neurotransmitter
Undersupply is linked to seizures, tremors and insomnia
Glutamate:
Major excitatory neurotransmitter involved in memory
Oversupply can overstimulate brain producing migraines or seizures (which is why some people avoid MSG monosodium glutamate in food)
Meningitis
Inflammation of the inner meninges (mostly pia and arachnoid) of the brain and spinal cord
Route of transmission: direct (aerosol, droplet secretion, direct contact with secretions, ear infections, nasopharynx, cranial injury), via the blood (septicemia) or viral meningitis (most common)
Bacterial meningitis is less common but high mortality especially high risk in infants
Cause varies with age, vaccination status (less than 4 years and unvaccinated) and other medical conditions
Meningococcus is most common cause of bacterial meningitis in UK (B, C subtypes)
In UK, syphilis, TB and fungal infections are rare causes
Klebsiella P account for most causes of hospital acquired meningitis (nosocomial infection)
Common causes:
Meningococcus (neisseria meningitidis)
Pneumococcus (streptococcus pneumonia)
Haemophilus influenzae
Types of meningitis
in addition to common classification according to microorganism cause
Aseptic meningitis - CSF has cells but is gram -ve and no bacteria can be cultured include viral and fungal causes
Non-infective meningitis (systemic disease) - inflammation due to infiltration of the meninges, such as malignant cells (leukemia, lymphoma) or rheumatological conditions (sarcoidosis or SLE)
Meningitis presentation
Very general in children: headache, fever, vomiting, malaise
Headache
Neck stiffness (nuchal rigidity)
Fever
Muscle ache/joint pain
Vomiting
Kernig’s sign: inability to fully extend knee when hip is flexed 90 degrees
Brudzinski’s sign: passive flexion of neck causes flexion of both legs and thighs
Papilloedema - swollen optic disc due to increased intracranial pressure
In meningococcal septicaemia - non-blanching petechiae and purpuric skin rash and signs of shock (this is a LATE sign due to septicaemia being present usually day 5 onwards)
Meningitis investigations
Diagnostic: lumbar puncture and laboratory CSF analysis
Bloods: FBC, CRP, blood cultures, blood glucose, ABG/VBG
KFT
Urine cultures
CXR (lung infections or abscesses)
CT (sometimes before LP) to exclude high intracranial pressure however NICE recommends clinical assessment NOT CT for this
Lumbar puncture complications and CIs
LP complications:
Coning (cerebral herniation)
Introduction of infection into CSF
CIs:
Local skin infection
Bleeding problems or anticoagulant therapy
Signs of spinal cord compression/pathology
Papilloedema or other signs of raised intracranial pressure
Suspicion of intracranial or cord mass
Congenital neurological lesions in lumbosacral region
Must have consultant present for LP with any CIs:
Raised ICP or reduced fluctuating loss of consciousness
Altered consciousness (GCS <9)
Focal neurological signs
Relative bradycardia and HTN
Abnormal posture
Unequal, dilated or poorly responsive pupil
Papilloedema
Shock
Coagulation abnormalities or therapy or platelet count <100x109/litre
Local superficial infection at LP site
Respiratory insufficiency in children
Normal CSF in adults
White and colourless
WBC: 0-5 cells/uL
No neutrophils, primarily lymphocytes
RBCs: 0-10/mm3
Protein: 0.15-0.45g/L (or <1% serum protein concentration)
Glucose: 2.8-4.2mmol/L (or >60% plasma glucose concentration)
Opening pressure: 10-20cm H2O
CSF overview in meningitis
Viral: clear, white cells high 5-1000, predominantly lymphocytes, normal RBCs <10, normal/high protein 0.4-1, normal glucose, normal/slightly high opening CSF pressure
Bacterial: cloudy and turbid look, very high white cells 100-50,000, neutrophils (PMN) predominately (some can cause leukocytes), high protein >1, decreased glucose <40%, high opening CSF pressure
TB meningitis: cloudy and viscous, increased white cells <500, mostly lymphocytes, very high protein 1-5, decreased BG <30%, high opening CSF pressure
FUNGAL MENINGITIS: clear/cloudy Elevated opening pressure Elevated WBC (10-500) Low glucose Elevated protein Gram stain positive Most likely causative organisms: cryptococcus neoformans and candida
Meningitis management
Urgent: all suspected meningitis cases are medical emergencies needing immediate hospitalisation
Suspected with rash - empirical antibiotics IM/IV benzylpenicillin (CI in severe allergy, give cefotaxime or ceftriaxone if allergy) blind therapy 1st line - targets meningococcal strain most common in UK
2nd choice antibiotics given when blood/CSF culture results are back (adult <50 - cefotaxime or ceftriaxone for 7-10 days, adult >50 cefotaxime or ceftriaxone + amoxicillin or ampicillin for 7-10 days)
Suspected without rash - urgent hospitalisation NO ANTIBIOTICS unless urgent transfer not possible
Suppurative treatment - analgesia, antipyretics, VI fluid (viral cause)
Identify signs of shock and sepsis an treat as needed
Dexamethasone (add on treatment before or with antibiotics within 12 hours)
Close contact prophylaxis - ciprofloxacin or rifampicin or IM ceftriaxone. People who have had prolonged close contact with case in household setting during 7 days before onset of illness (healthcare workers don’t need unless direct exposure of mouth/nose to infectious droplets with patient with <24 hours antibacterial treatment)
Notification of health protection unit (notifiable disease)
Meningitis complications
Much higher in meningococcal septicaemia (up to 57%)
Cerebral infarction in 1 in 4 people with bacterial meningitis
Neurological complications: hearing loss (higher in infants and children), seizures, cognitive impairment, motor deficits, visual impairments
Hydrocephalus
Learning difficulties
Encephalitis
Inflammation of the brain
Mostly caused by viral or post-infectious due to autoimmune disease
Causes:
Viral: HSV-1, CMV, EBV, VZV, HIV, measles, mumps, rabies, enterovirus
Bacterial: all causes of bacterial meningitis including TB, mycoplasma and listeria
Fungal and parasitic infections
Encephalitis presentation
Fever Headache Neck stiffness Vomiting Altered consciousness Convulsions Focal neurological signs Signs of raised intracranial pressure Psychiatric symptoms
Encephalitis investigations
CSF analysis for HSV-1 or 2, VZV and enteroviruses: usually shows moderate protein increase, raised lymphocytes, CSF/glucose ratio normal
FBC, blood cultures, renal function, U+Es, LFTs, glucose, ESR, CRP
CT scan for lesion/tumour, raised ICP (DOES NOT RULE OUT DIAGNOSIS)
MRI scan to detect demyelination and oedematous changes
Encephalitis management and complications
Urgent hospital admission
Parenteral antibiotics if suspected meningitis (IV/IM benzylpenicillin)
Immediate treatment with IV acyclovir (improves prognosis) +/- antibiotics to treat secondary bacterial infection
Careful IV fluid administration as this can worsen cerebral oedema
Complications: Mortality 70% in 7-10 days if untreated SIADH Disseminated Intravascular Coagulation Epilepsy Complications are usually linked to affected area of brain
Tuberculosis meningitis
Pathology:
Haematogenous spread eg miliary TB, foci of infection in brain and spinal cord
Foci can enlarge forming tuberculomas - foci rupture leads to meningitis
Active TB:
Containment by immune system by T cells and macrophages is inadequate
TB contagious
Either primary infection or reactivation of latent TB
Latent TB:
Granuloma formation prevents bacterial growth and spread - persistent immune system contaminant
Skin or blood testing (TBT, IGRAS) are positive - infection exists but sputum/CXR are normal - patient is asymptomatic and non-infectious
TB meningitis risk factors and presentation
Immunosuppression
HIV/AIDS
Alcoholism
Age <3 YO
Presentation: Headache Meningism Confusion FND Seizures Systemic symptoms: fever, night sweats, anorexia, weight loss and malaise
TB meningitis investigations
LP and CSF analysis: leukocytosis, raised protein, CSF plasma glucose <50%,
NAAT in CSF
AFB stain
PCR and culture
Serologic HIV test
CT/MRI may show hydrocephalus or Tuberculomas
general testing - tuberculin skin testing or IGRAS testing (more sensitive for BCG vaccination)
Management of TB meningitis
Rifampicin 2 months intensive 4 months continuation - p450 inducer: warfarin, calcineurin inhibitors, oestrogen etc. body secretion can coloured orange or red, altered liver function
Isoniazid 2mths intensive 4mths continued - risk of peripheral neuropathy and hepatitis, give with prophylactic pyridoxine,
Pyrazinamide 2 mths intensive - hepatotoxicity risk, measure eGFR before
Ethambutol 2mths intensive - may cause colour blindness and poor visual acuity must check visual acuity before starting and monitor monthly and eGFR
Shingles
VZV varicella zoster virus, form of herpes virus
In children: respiratory droplets containing virus enter lungs and incubate for 14-21 days. Invasion to respiratory mucosa, disseminates via mononuclear cells to skin. Virus containing vesicles causes CHICKEN POX, remains dormant in sensory nerve roots for years
In adults: reactivation of VZV but this time is limited to a dermatome of the skin = SHINGLES
Shingles is less contagious than varicella - household transmission rate is 15%
Blood test for antibodies can confirm is ever had chickenpox before
Those exposed to VZV if never had chickenpox before will get chicken pox no matter what age, but those who have HAD chickenpox will get shingles if reexposed
Presentation of shingles
Painful, burning, numbness in area in prodromal period
Few days later shows macular vesicular rash in SINGLE DERMATOME
Most common sites: lower thoracic dermatomes and ophthalmic division of trigeminal nerve V1 (ocular shingles)
Rash is still infectious until lesions dry and become crusted