Showing posts with label Neurology. Show all posts
Showing posts with label Neurology. Show all posts
Caisson Disease or Decompression Sickness
Caisson disease is also known as decompression sickness or diver's disease. When the body is subjected to high surrounding pressure (e.g. scuba diving), more than usual amount of Nitrogen gets dissolved in the blood. If the pressure is relieved suddenly, the dissolved Nitrogen can become gaseous quicker than the body can get rid of. These bubbles can lead to ischemia by blocking blood vessels. Clinical situations when such sudden depressurization can occur include scuba diving, caisson working, mining, flying in unpressurised aircraft, and extra-vehicular activity from spacecraft.
Depending upon the location of ischemia a variety of symptoms can results. Classically the symptoms are described as the bends, the chokes and the staggers!
The bends: refers to pain in the joints from ischemia of joint capsules
The chokes: refers to dyspnea
The staggers: refers to neurological symptoms.
Prevention:
-Divers should limit their ascent rate to about 10 metres per minute.
-Oxygen pre-breathing
Treatment:
-Administer 100% oxygen by face mask until re-compression with 100% oxygen until hyperbaric oxygen therapy is available.
-Treat dehydration
USMLE Ethics Question 3
Q: John is a 55 year old man who works as a bus driver for the city of Washington DC. He had a stroke 6 months ago from which recovered well except that he has had 2 seizures in last 4 months and has focal damage on an MRI from the stroke. As his physician you believe that he is at risk of having more seizures and you have started him on antiepileptics. He requests his doctor not to mention his seizures to his employer as this may result in loss of his job and he is the sole earner in his family. What should you do?
A: Try to convince him to tell his employer. If he refuses you have to inform the appropriate the authorities because you have a duty towards him as well as the society.
Spinal Canal Stenosis
Usually results from degenerative changes in the lumbar vertebrae. Predisposing factors include older age, history of back injury or surgery, and manual labor.
Clinical features: Leg pain (neurogenic claudication) and paresthesia that comes on while walking or running and gets better on rest.
Diagnosis: Imaging will show degenerative changes and spondylolisthesis (Sliding of one vertebra over another). MRI is diagnostic.
Treatment: Symptomatic with NSAIDs and physical therapy. Steroid injections(epidural) are rarely used if other methods fail. If features of cord compression are present surgery may be needed.
Clinical features: Leg pain (neurogenic claudication) and paresthesia that comes on while walking or running and gets better on rest.
Diagnosis: Imaging will show degenerative changes and spondylolisthesis (Sliding of one vertebra over another). MRI is diagnostic.
Treatment: Symptomatic with NSAIDs and physical therapy. Steroid injections(epidural) are rarely used if other methods fail. If features of cord compression are present surgery may be needed.
Febrile seizures
A febrile seizure is defined by the following:
-3 months and 5 years of age
-associated with fever but without evidence of intracranial infection.
-Seizures with fever in children with history of nonfebrile seizures are excluded.
Typical febrile seizures:
-Lasts <15 minutes
-Occurs no more than once in 24 hours
-Is generalized tonic clonic
Lumbar puncture is Indicated only to rule out meningitis or encephalitis if signs or symptoms suggestive of these illnesses are present.
Treatment of simple/typical febrile seizures:
Treat the cause of fever (most are viral infections and do not require antibiotics). Antipyretics are used in adequate amounts until the risk of fever abates. Antipyretics are of no direct value in preventing febrile seizures or their recurrence nor do they slow temperature elevation during fever.
-3 months and 5 years of age
-associated with fever but without evidence of intracranial infection.
-Seizures with fever in children with history of nonfebrile seizures are excluded.
Typical febrile seizures:
-Lasts <15 minutes
-Occurs no more than once in 24 hours
-Is generalized tonic clonic
Lumbar puncture is Indicated only to rule out meningitis or encephalitis if signs or symptoms suggestive of these illnesses are present.
Treatment of simple/typical febrile seizures:
Treat the cause of fever (most are viral infections and do not require antibiotics). Antipyretics are used in adequate amounts until the risk of fever abates. Antipyretics are of no direct value in preventing febrile seizures or their recurrence nor do they slow temperature elevation during fever.
Botulism
Botulism is caused by a gram positive rod Clostridium botulinum. The toxin released by this bacteria binds irreversibly to the presynaptic membranes of peripheral neuromuscular and autonomic nerve junctions. This binding inhibits acetylcholine release, causing weakness and flaccid paralysis. The paralysis persists until the nerve endings regenerate.
The 3 types of botulism are as follows:
Infant botulism is caused by ingested spores of the bacteria which germinate in the gut releasing toxin inside the body.
Wound botulism results from contamination of a wound with toxin-producing clostridia.
Foodborne botulism occurs after consumption of contaminated food for e.g. canned vegetables.
Key points for USMLE:
-The binding of toxin is irreversible
-Infant botulism is associated with consumption of honey
Differential diagnosis of botulism:
* Guillain-Barré syndrome
* Myasthenia gravis
* Lambert-Eaton myastheic syndrome
* Polio
* Tick paralysis
* Stroke
* Diphtheric paralysis
* Congenital neuropathy or myopathy
* Snake bite (Cobra)
The 3 types of botulism are as follows:
Infant botulism is caused by ingested spores of the bacteria which germinate in the gut releasing toxin inside the body.
Wound botulism results from contamination of a wound with toxin-producing clostridia.
Foodborne botulism occurs after consumption of contaminated food for e.g. canned vegetables.
Key points for USMLE:
-The binding of toxin is irreversible
-Infant botulism is associated with consumption of honey
Differential diagnosis of botulism:
* Guillain-Barré syndrome
* Myasthenia gravis
* Lambert-Eaton myastheic syndrome
* Polio
* Tick paralysis
* Stroke
* Diphtheric paralysis
* Congenital neuropathy or myopathy
* Snake bite (Cobra)
EEG findings in Absense seizures/ Petit mal epilepsy
Electroencephalographic findings in typical absence seizures (petit mal epilepsy) are as follows:
1) Background activity is normal.
2) Frontally dominant bursts of 3-Hz spike-and-wave complexes are seen during the seizures.
3) In syndromes with less frequent absence seizures (juvenile absence epilepsy or juvenile myoclonic epilepsy), an awake recording may be normal; a sleep or sleep-deprived recording may show evidence of generalized 3-Hz spike-and-wave complexes.
4) There is abrupt onset and ending. No postictal EEG slowing is noted.
5) Video EEG may demonstrate that clinical seizures at times occur after the the start of ictal EEG activity by a few seconds.
1) Background activity is normal.
2) Frontally dominant bursts of 3-Hz spike-and-wave complexes are seen during the seizures.
3) In syndromes with less frequent absence seizures (juvenile absence epilepsy or juvenile myoclonic epilepsy), an awake recording may be normal; a sleep or sleep-deprived recording may show evidence of generalized 3-Hz spike-and-wave complexes.
4) There is abrupt onset and ending. No postictal EEG slowing is noted.
5) Video EEG may demonstrate that clinical seizures at times occur after the the start of ictal EEG activity by a few seconds.
Common paraneoplastic syndromes
Paraneoplastic Limbic Encephalitis :
PLE is characterized by irritability, seizures, short-term memory loss and depression. MRI reveals bilateral mesial temporal lobe hyperintensities on T2 weighted images. Small cell lung carcinoma is the most common associated cancer.
Paraneoplastic Cerebellar Degeneration :
PCD patients present with cerebellar signs. MRI may be normal in initial stages. Common malignancies associated with this syndrome include -Small cell lung cancer, ovarian cancer, breast cancer and Hodgkin's lymphoma.
Paraneoplastic Encephalomyelitis :
In this condition there is patchy inflammation involving multiple areas of the nervous system. The tumor most frequently involved is again Small Cell Lung Carcinoma.
Paraneoplastic Sensory Neuropathy :
It is usually sensory neuropathy.
Opsoclonus-myoclonus :
This syndrome usually affects young children. While 50% of children with this syndrome have neuroblastoma only about 2% of children with this tumor develop opsoclonus.
Lambert-Eaton Myasthenic Syndrome (LEMS):
This is a Neuromuscular junction disorder characterized by Acetylcholine release problems from the presynaptic terminal.Symptoms are similar to myasthenia gravis. Diagnosis is often made using EMG. LEMS results from immunologic attack against the presynaptic terminal that cause interference with the release of Acetylcholine.
Foster Kennedy Syndrome
Foster Kennedy Syndrome is one-sided optic atrophy with contralateral optic disc swelling. It is typically due to a frontal lobe tumor (usually an olfactory groove meningioma) which compresses the ipsilateral optic nerve causing its atrophy and also raises the intracranial pressure leading to contralateral papilledema. The patient may present with anosmia and frontal lobe signs alongside the visual symptoms (central scotoma).
In the absence of intracranial mass, the above mentioned findings are named pseudo- Foster Kennedy Syndrome. It is classically due to bilateral sequential optic neuritis/ischemic optic neuropathy
In the absence of intracranial mass, the above mentioned findings are named pseudo- Foster Kennedy Syndrome. It is classically due to bilateral sequential optic neuritis/ischemic optic neuropathy
Sydenham's Chorea
Q: In Sydenham's Chorea (post streptococcal infection) what is the histopathology of the brain likely to show?
A: Necrotizing arteritis of the caudate, putamen & thalamus
Risk factors for stroke
Hypertension is the most important modifiable risk factor for stroke. (not smoking, DM, lipids or obesity)
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