Brain Lesions Flashcards
Herpes Simplex Encephalitis
Herpes simplex (HSV) encephalitis is a common topic in the exam. The virus characteristically affects the temporal lobes - questions may give the result of imaging or describe temporal lobe signs e.g. aphasia
Features
fever, headache, psychiatric symptoms, seizures, vomiting
focal features e.g. aphasia
peripheral lesions (e.g. cold sores) have no relation to presence of HSV encephalitis
Pathophysiology
HSV-1 responsible for 95% of cases in adults
typically affects temporal and inferior frontal lobes
Investigation
CSF: lymphocytosis, elevated protein
PCR for HSV
CT: medial temporal and inferior frontal changes (e.g. petechial haemorrhages) - normal in one-third of patients
MRI is better
EEG pattern: lateralised periodic discharges at 2 Hz
Mx - IV ACICLOVIR
The prognosis is dependent on whether aciclovir is commenced early. If treatment is started promptly the mortality is 10-20%. Left untreated the mortality approaches 80%
Foster-Kennedy Syndrome
Foster-Kennedy syndrome describes a series of symptoms and signs associated with frontal lobe lesions.
Features optic atrophy in the ipsilateral eye papilloedema in the contralateral eye central scotoma in the ipsilateral eye anosmia
The combination of an ipsilateral optic atrophy and contralateral papilloedema is a MRCP favourite: Foster-Kennedy syndrome, typically caused by a frontal lobe mass, normally a meningioma, which compressing on the ipsilateral optic nerve and olfactory nerve, while increasing intracranial pressure for the contralatral optic nerve sheath.
Foster-Kennedy Syndrome - Example Question
A 67 year old male presents to your neurology clinic with his wife, reporting a 3 month history of worsening vision in his left eye. He is very reluctant to seek any medical help but says that a number of factors have finally convinced him to attend.
Over the past 2 months, he reports a constant and worsening headache, worse at night and with coughing. He has occasionally felt extremely nauseated and vomited on a number of occasions, at least twice waking him from sleep. His wife also notes significant personality change: her husband is a retired farmer who prides him on being a stoic man. She notes that he has become increasingly emotional and occasionally aggressive, which she puts down however to struggling with his symptoms. Prior to these symptoms starting 3 months ago, he has always been fit and well with no past medical or drug history.
On examination, you note a left relative afferent papillary defect with equally sized pupils. Visual acuity in the left eye is 6/60 and 6/9 on the right. Testing of colour vision with Ishihara plates demonstrate 0/17 on the left and 17/17 on the right. A central scotoma is found in the left eye. Fundoscopy of the left eye reveals a pale optic disc with poor vasculature while the right appears swollen. A full range of painless eye movements is demonstrated. The remaining examination of the cranial nerves, upper and lower limbs are unremarkable. Bloods are unremarkable, a MRI head is awaited.
What is the most likely diagnosis?
> Foster-Kennedy syndrome Idiopathic intracranial hypertension (IIH) Multiple sclerosis (MS) Fronto-temporal dementia Age related macular degeneration (ARMD)
This is a difficult question requiring recognition of a high pressure headache, left optic atrophy and contralateral swollen disc secondary to papilloedema. The combination of an ipsilateral optic atrophy and contralateral papilloedema is a MRCP favourite: Foster-Kennedy syndrome, typically caused by a frontal lobe mass, normally a meningioma, which compressing on the ipsilateral optic nerve and olfactory nerve, while increasing intracranial pressure for the contralatral optic nerve sheath.
Idiopathic intracranial hypertension may present asymmetrically but typically produces bilateral disc swelling. It is conceivable the patient has multiple sclerosis with optic atrophy as a sequalae of left optic neuritis, followed by a second episode of contralateral optic neuritis presenting as papillitis, inflammation of the optic nerve head. This is unlikely with only one episode of visual dysfunction described with a insidious progressive onset.
Fronto-temporal dementia may explain the behavioural changes but does not account for visual symptoms.
Lastly, age related macular degeneration can mimic papillitis on fundoscopy, with deposition of drussen making the optic disc ‘look’ swollen. However, the deposition of these retinal cell byproducts is generally more diffuse across the retina, with wet ARMD also displaying abnormal retinal vasculature. While retinal atrophy may be present, it does not typically produce optic atrophy.
Brainstem Lesions
Medial Thalamus and mamillary bodies of the hypothalamus > WERNICKE and KORSAKOFF SYNDROME
Subthalamic nucleus of the Basal Ganglia > HEMIBALLISM
Striatum (Caudate Nucleus) of the Basal ganglia > HUNGTINGON CHOREA
Substantia Nigra of the Basal Ganglia > PARKINSON’S DISEASE
Amygdala > KLUVER-BUCY SYNDROME (Hypersexuality, Hyperorality, Hyperphagia, Visual Agnosia)
Parietal Lobe Lesions
- Sensory Inattention
- Apraxias - inability to perform purposeful actions
- Stereognosis (tactile agnosia) - inability to identify an object by active touch of hands
- Inferior homonymous quadrantanopia (PITS)
- Gertsmann’s Syndrome (lesion of dominant parietal) = ALEXIA, ACALCULIA, FINGER AGNOSIA, Right-Left Disorientation
Finger Agnosia = loss in the ability “to distinguish, name, or recognize the fingers’
Frontal Lobe Lesion
- Expressive (Broca’s) aphasia: located on posterior aspect of frontal lobe, in the inferior frontal gyrus. SPEECH becomes non-fluent, laboured and halting = expressive aphasia
- Disinhibition
- Perseveration
- Anosmia
- Inability to generate a list
Temporal Lobe Lesion
- Wernicke’s aphasia - this area ‘forms’ the speech before sending it to Broca’s Lesions result in word substitution, neologisms but speech remains fluent
- Superior homonymous quadrantanopia (PITS)
- Auditory agnosia (inability to be able to differentiate between certain sounds)
- Prosopagnosia (Difficulty recognising faces)
Occipital Lobe Lesion
- Homonymous Hemianopia (with macula sparing)
- Cortical blindness
- Visual Agnosiaa (condition in which a person can see but cannot recognize or interpret visual information)
