MRCP revision battle 30.1: Retinitis Pigmentosa

Today is the start of a 3 day neuro/opthalmology blitz, so hold on to your hats....


MRCP revision battle 30.1: Retinitis Pigmentosa
MRCP revision battle 30.2: Oculogyric Crisis
MRCP revision battle 30.3: Myotonic Dystrophy
MRCP revision battle 30.4: Trinucleotide repeat disorders
MRCP revision battle 30.5: Huntington's Chorea
MRCP revision battle 30.6: Friedreich's ataxia
MRCP revision battle 30.7: Alzheimer's Disease




MRCP revision battle 30.1: Retinitis Pigmentosa

Retinitis pigmentosa is a type of progressive retinal dystrophy which eventually leads to blindness.

It has a very characteristic fundoscopic appearence with black mottling of the retina and a pale optic disc, as illustrated below in an image by Christian Hammel (from wiki commons):

It can be inherited in an autosomal dominant, autosomal recessive or X linked recessive fashion.



Night blindness is often the first sign.
Later comes funnel/tunnel vision.


It is associated with many conditions, including:

• Kearns Sayre (remember battle 15.1?)
• Ushers syndrome = retinitis pigmentosa with sensorineural deafness
• congenital toxoplasmosis

There is no cure for retinitis pigmentosa but progression of the disease can be slowed by vitamin A.



On to the second battle of the day...

MRCP revision battle 30.2: Oculogyric Crisis

The key features of an oculogyric crisis are restlessness and upward deviation of the eyes (although this only occurs in severe cases).


Oculogyric crises may be precipitated by a range of drugs including:

• neuroleptics
• metoclopramide/domperidone
• nifedipine
• TCA
• carbamazepine

Several clinical conditions can also cause oculogyric crises, for example:

• parkinsons disease
• post encephalitis
• bilateral thalmic infarction
• MS

Treatment is with procyclidine, an anticholinergic.


On to the next battle...

MRCP revision battle 30.3: Myotonic Dystrophy

Myotonic dystrophy is an autosomal dominant condition in which there is muscle weakness and myotonia.  It is a trinucleotide repeat disorder.

Onset tends to be in the 30s.


There are 2 types:


Dystrophia myotonica (=DM) 1

• 98% of cases
• more severe
• distal muscle weakness
• chromosome 19

Dystrophia myotonica 2:

• 2% of cases
• less severe
• proximal muscle weakness
• chromosome 3

Features associated with myotonic dystrophy include:

• long faces
• frontal baldness
• myotonia and weakness
• testicular/ovarian atrophy
• bilateral ptosis
• cateract
• cardiomyopathy
• diabetes
• miotic pupils 
• mildly decreased IQ

It is incurable but phenytoin can improve the myotonia.


Lets move on to consider an overview of trinucleotide repeat disorders

MRCP revision battle 30.4: Trinucleotide repeat disorders

Trinucleotide repeat disorders are conditions in which 3 nucleotides in the DNA are expanded.

The most 'famous' are:

• Huntingtons chorea (CAG) - covered in next battle
• Fragile X (CGG)
• Myotonic dystrophy (CTG) - covered in previous battle
• Friedreichs ataxia (GAA) - covered in battle 30.6

Two concepts to be born in mind for trinucleotide repeat disorders are:

Anticipation = the disease presents earlier and is worse in successive generations

Somatic instability = expansion increases as patient gets older


So lets briefly cover the most famous, Huntingtons...

MRCP revision battle 30.5: Huntington's Chorea

Huntington's chorea is an autosomal dominant condition due to CAG repeats.

It is carried on chromosome 4.


Symptoms tend to start in the 40s with a progression from chorea to irritability to dementia and death.


There is no cure.  The chorea may be treated with a dopamine antagonist such as tetrabenazine.



Note that Hunington's has complete penetrance so a child of a sufferer has a 50% chance of being affected.  Due to anticipation if they are affected they are also likely to develop symptoms earlier.



Next up: Friedreich's ataxia...

MRCP revision battle 30.6: Friedreich's ataxia

Friedreichs ataxia is an autosomal recessive trinucleotide repeat disorder (GAA)


It causes degeneration of nerve tracts resulting in cerebellar ataxia, dysarthria, nystagmus and dysdiadocholokinesis.


Muscles are weak, reflexes are depressed but plantars are upgoing.


There is often scoliosis and high arches of the feet.

Cardiomyopathy is another complication.


There is no cure.


Lets now try and forget all these incurable diseases with a touch of Alzheimer's...

MRCP revision battle 30.7: Alzheimer's Disease

Alzheimer's disease is the leading cause of dementia.  This battle aims to pick out a few juicy facts for MRCP; http://alzheimers.org.uk/ can provide more in-depth information if you are interested.


The earliest symptom of AD is typically forgetfulness.



5% of cases are autosomal dominant, with chromosomes 1, 14, 19 and 21 implimented.

After age, apoE4 (chromosome 19) is the most significant risk factor for AD.


Beta amyloid plaques and hyperphosphorylated tau protein tangles are found within neurones post-mortem.
The density of the tangles can correlate with the severity of the dementia.




Hippocampal atrophy is prominant.





Cholinesterase inhibitors such as donepezil, rivastigmine and galantamine are licensed for patients with a MMSE of between 10 and 20.

Memantine (an antiglutamatergic) may be useful in severe AD.



As Bugs Bunny would say, thhhhatttttts alll folllkkkksss.... until tomorrow!