Neurology Flashcards
Describe the pathophysiology behind Alzheimer’s Disease.
A progressive degeneration of the cerebral cortex. Neurons affected develop surrounding amyloid plaques, neurofibrillary tangles, and produce less acetylcholine.
How is Alzheimer’s Disease treated pharmacologically?
AChE inhibitors appear to be beneficial for people with mild to moderate Alzheimer’s disease.
Memantine is cost-effective in the management of moderate and severe Alzheimer’s disease
Give example AChE inhibitors
Donepezil, galantamine, rivastigmine
How do AChE inhibitors work?
Anticholinesterases are a class of drugs that decrease breakdown of acetylcholine (a chemical messenger in the brain) and can be used in conditions whereby there is an apparent lack of this messenger transmission such as in Alzheimer’s disease.
How is narcolepsy treated pharmacologically?
First-line is modafinil (but note subsequent MHRA warnings).
Second-line is methylphenidate.
What is modafinil? When can it not be used?
Treats excessive daytime sleepiness, multiple contra-indications
What is methylphenidate?
A stimulant - has many side effects
How is cataplexy treated pharmacologically?
Sodium oxybate (first line), and/or antidepressants
Why do we avoid tricyclics in Alzheimer’s care?
Because they, and anticholinergics, can worsen cognitive decline
Describe the triad of Wernicke’s encephalopathy
Ophthalmoplegia, global confusion, gait ataxia
What is Korsakoff Syndrome?
Wernicke’s enceph + amnesia leading to confabulation
Describe the pathophysiology behind Korsakoff Syndrome
The mamillary bodies are affected in the limbic system, so pts confabulate stories to fill in the gaps
How do we treat Wernicke’s encephalopathy?
Wernicke’s encephalopathy is a medical emergency. Thiamine orally (IM or IV may be used in secondary care) plus vitamin B complex or multivitamins.
LMN vs. UMN: Where would you find disuse atrophy?
UMN: if you don’t use it you lose it (can’t willingly activate muscle). Loss of 15-20%.
LMN vs. UMN: Where would you find denervation atrophy?
LMN: lack of LMN stimulation leads to reduced ACh secretion. This reduces muscle contraction, and reduces activation of an intracellular pathway that produces TFs, which would increase protein synthesis. The decreased protein synthesis leads to increased proteolysis, so the muscle breaks down. Loss of up to 70-80%.
What are fasciculations?
Pathological muscle contraction seen with LMN lesions, similar to a muscle twitch
Describe the pathophysiology behind fasciculations
Reduced ACh in the synaptic cleft leads to decreased activity of ACh receptors on the muscle, which leads to upregulation of the ACh receptors (more are made). This shifts the resting potential closer to the threshold potential, so it is easier to mechanically activate the chemically-gated ACh receptors, leading to pathological muscle contraction.
What are fibrillations?
Fasciculations but seen on an EMG
Why is there hypertonia in UMN lesion?
The medullary reticulospinal nuclei aren’t triggered, so the LMN isn’t inhibited, and there is increased alpha motor neuron activity to the extrafusal fibres - increasing their tone.
Why is there hyperreflexia in UMN lesion?
The medullary reticulospinal nuclei aren’t triggered, so the LMN isn’t inhibited, and there is increased gamma motor neuron activity to the intrafusal fibres - increasing the sensitivity of the muscle spindles, leading to hyperreflexia.
What is spastic paralysis?
Loss of muscle strength due to the combined effects of hypertonia and hyperreflexia in UMN lesion
What is the difference between spasticity and rigidity?
Spasticity is velocity dependant - it increases with speed - and is unidirectional. Rigidity is velocity independent, and is bidirectional.
What is the clasp-knife phenomenon?
Clasp-knife response refers to a Golgi tendon reflex with a rapid decrease in resistance when attempting to flex a joint. Seen in UMN lesion.
What is flaccid paralysis?
Loss of muscle strength due to hypotonia and hyporeflexia - seen in LMN lesion
Why do you see the Babinski reflex with UMN lesions?
The corticospinal tract inhibits the reflex causing dorsiflexion of the foot. When this inhibition is no longer present, this reflex is hyperreactive. They become so hyperreactive that the dorsiflexors overcome the plantar-flexors, and the foot then dorsiflexes instead of plantar-flexes.
Where do you see Babinski reflexes other than with UMN lesions?
In children typically less than one year old. The corticospinal tract should be heavily myelinated, but this myelination is developing in v. young children.
What is Hoffman’s sign?
The Hoffman sign is an involuntary flexion movement of the thumb and or index finger when the examiner flicks the fingernail of the middle finger down.
Where do you see pronator drift?
UMN lesion
What is neurofibromatosis?
A genetic condition that causes nerve tumours (neuromas) to develop throughout the nervous system. These tumours are benign, however they do cause neurological and structural problems
What is the NF1 gene?
The neurofibromatosis type 1 gene is found on chromosome 17. It codes for a protein called neurofibromin, which is a tumour suppressor protein.
How do we diagnose type one neurofibromatosis?
CRABBING, 2 of the following 7: Cafe-au-lait spots (6 or more), relative with NF1, axillary or inguinal freckles, bony dysplasia such as bowing of a long bone or sphenoid wing dysplasia, iris hamartomas (Lisch nodules) (2 or more) are yellow brown spots on the iris, neurofibromas (2 or more) or 1 plexiform neurofibroma, glioma of the optic nerve. Good luck.
How do we treat neurofibromatosis?
Management of symptoms, not direct treatment
Where do you see bilateral acoustic neuromas?
Type 2 neurofibromatosis. Acoustic neuromas lead to hearing loss, tinnitus and balance problems.
What pattern of inheritance does NF1 show?
Inheritance of mutations in this gene is autosomal dominant
What is motor neurone disease?
Motor neurone disease is a progressive, ultimately fatal condition where the motor neurones stop functioning. There is no effect on the sensory neurones and patients should not experience any sensory symptoms.
Describe the pathophysiology of MND
Mechanism not understood. There is progressive degeneration of both upper and lower motor neurones. The sensory neurones are spared.
What is dysarthria?
Slurred speech
How is MND treated?
Best tx is riluzole at the moment. Slows progression of the disease. Can extend life by a few months in AML.
How does MND present?
The typical patient is a late middle aged man, possibly with an affected relative. There is an insidious, progressive weakness of the muscles throughout the body affecting the limbs, trunk, face and speech. The weakness is often first noticed in the upper limbs. There may be increased fatigue when exercising. They may complain of clumsiness, dropping things more often or tripping over. They can develop slurred speech (dysarthria). UMN & LMN signs.
What is multiple sclerosis?
A chronic and progressive condition that involves demyelination of the myelinated neurones in the central nervous system
Describe the epidemiology of MS.
MS typically presents in young adults (under 50 years) and is more common women. Symptoms tend to improve in pregnancy and in the postpartum period.
Describe the pathophysiology of MS.
Oligodendrocytes create myelin in the CNS (Schwann cells = PNS). There is inflammation around myelin in the CNS and infiltration of immune cells that cause damage to the myelin.
How is MS diagnosed?
MRI: multiple lesions disseminated in time and space”
Give four causes of MS.
Epstein-Barr Virus, genetics, low VitD, smoking, obesity
How does MS present?
Optic neuritis, eye movement abnormalities, focal weakness, focal sensory symptoms, ataxia
Describe the eye movement abnormalities sometimes seen in MS.
Unilateral lesions in the sixth nerve causes a condition called internuclear ophthalmoplegia. Internuclear refers to the nerve fibres that connect between the cranial nerve nuclei that control eye movements (3rd, 4th and 6th cranial nerve nuclei). The internuclear nerve fibres are responsible for coordinating the eye movements to ensure the eyes move together. Ophthalmoplegia means a problem with the muscles around the eye.
Lesions in the sixth cranial nerve cause a conjugate lateral gaze disorder. Conjugate means connected. Lateral gaze is where both eyes move together to look laterally to the left or right. It is disordered in a sixth cranial nerve palsy. When looking laterally in the direction of the affected eye, the affected eye will not be able to abduct. For example, in a lesion affecting the left eye, when looking to the left, the right eye will adduct (move towards the nose) and the left eye will remain in the middle as the muscle responsible for making it move laterally is not functioning.
If a patient with MS had a LP, what might you see in the CSF?
Oligoclonal bands
How does optic neuritis present?
Central scotoma. This is an enlarged blind spot.
Pain on eye movement
Impaired colour vision
Relative afferent pupillary defect
How do we treat relapses of MS?
Relapses can be treated with steroids. NICE recommend methylprednisolone.
How do we treat spasticity?
Baclofen, gabapentin and/or physiotherapy
How do we treat urge incontinence pharmacologically?
Anticholinergic medications such as tolterodine or oxybutynin
How can we treat neuropathic pain pharmacologically?
Amitriptyline or gabapentin
What is hydrocephalus?
Cerebrospinal fluid (CSF) building up abnormally within the brain and spinal cord. This is a result of either over-production of CSF or a problem with draining or absorbing CSF.
Describe the physiology of the production of CSF.
CSF is created in the four choroid plexuses (one in each ventricle) and by the walls of the ventricles. CSF is absorbed into the venous system by the arachnoid granulations.
What is the most common cause of hydrocephalus? Describe its pathophysiology.
Aqueductal stenosis, leading to insufficiency drainage of CSF. The cerebral aqueduct that connects the third and fourth ventricle is stenosed (narrowed). This blocks the normal flow of CSF out of the fourth ventricle, causing CSF to build up in the lateral and third ventricles.
How does hydrocephalus present in children?
The cranial bones in babies are not fused at the sutures until around 2 years of age. Therefore, the skull is able to expand to fit the cranial contents. When a baby has hydrocephalus it causes outward pressure on the cranial bones. Therefore, babies with hydrocephalus will have an enlarged and rapidly increasing head circumference (occipitofrontal circumference).
How is hydrocephalus treated?
Placing a VP shunt that drains CSF from the ventricles into another body cavity is the mainstay of treatment for hydrocephalus. Usually the peritoneal cavity is used to drain CSF, as there is plenty of space and it is easily reabsorbed. Typically need replacing in children after 2 years.
What is normal pressure hydrocephalus?
The condition of ventricular dilatation in the absence of raised CSF pressure on lumbar puncture
How does normal pressure hydrocephalus present?
A triad of gait abnormality, urinary (usually) incontinence and dementia
Describe the epidemiology of NPH.
The condition occurs mainly in elderly patients, increasing in prevalence with age
Why do you find gait abnormalities in NPH?
Due to distortion of the corona radiata by the dilated ventricles. This area contains the sacral motor fibres than innervate the legs
Why do you find urinary incontinence in NPH?
Due to involvement of the sacral nerve supply that innervates the sphincter
Why do you see dementia in NPH?
Due to distortion of the periventricular limbic system. Slower onset than AD.
Give causes of increased intracranial pressure.
Malignancy, haematoma, abscess, oedema, venous obstruction, idiopathic
How does raised ICP present?
Headache, swollen optic disc, vomiting, mental state changes,
How do we investigate raised ICP?
CT/MRI to determine if there’s any underlying lesions, BCG, renal function, U&E, FBC
What are the priorities when treated raised ICP in the emergency setting?
In the acute emergency situation the priority is maintaining adequate arterial oxygen tension and ensuring normal vascular volume and normal osmosis. It is also essential to maintain normoglycaemia. Otherwise treatment depends on cause.
Give tx for raised ICP in the emergency setting.
Avoid pyrexia (raises ICP), manage seizures, CSF drainage, elevate head of bed, analgesia,
Give the five branches of the facial nerve
Temporal, zygomatic, buccal, marginal mandibular, cervical
What are the three functions of the facial nerve?
Motor: Supplies the muscles of facial expression, the stapedius in the inner ear and the posterior digastric, stylohyoid and platysma muscles in the neck.
Sensory: carries taste from the anterior 2/3 of the tongue.
Parasympathetic: it provides the parasympathetic supply to the submandibular and sublingual salivary glands and the lacrimal gland (stimulating tear production).
How do you distinguish between UMN and LMN facial lesion?
Each side of the forehead has upper motor neurone innervation by both sides of the brain. Each side of the forehead only has lower motor neurone innervation from one side of the brain.
In an upper motor neurone lesion, the forehead will be spared and the patient can move their forehead on the affected side.
In a lower motor neurone lesion, the forehead will NOT be spared and the patient cannot move their forehead on the affected side.
What is Bell’s Palsy?
An idiopathic condition presenting as a unilateral lower motor neurone facial nerve palsy. Recovery takes from several weeks to a year
How do we treat Bell’s Palsy?
If they present within 72hrs of symptom onset, treat with prednisolone. Patients also require lubricating eye drops to prevent the eye on the affected drying out and being damaged.
What is Ramsay-Hunt syndrome?
Caused by the herpes zoster virus, it presents as a unilateral lower motor neurone facial nerve palsy.
Give symptoms/signs of RH syndrome.
Patients stereotypically have a painful and tender vesicular rash in the ear canal, pinna and around the ear on the affected side. This rash can extend to the anterior 2/3 of the tongue and hard palate.
How is RH syndrome treated?
Prednisolone and acyclovir, lubricating eye drops