Neurology: Hydrocephalus, Abnormal Head Shapes & Muscular Dystrophy Flashcards
What is hydrocephalus?
Describes CSF building up abnormally within the brain and spinal cord.
This is a result of either:
a) over production of CSF, or
b) problem with draining or absorbing of CSF
How many ventricles are there in the brain?
4:
- two lateral
- the third
- the fourth
What is CSF produced by?
The 4 choroid plexuses (one in each ventricle) and by the walls of the ventricles.
What is CSF absorbed by?
Absorbed into the venous system by the arachnoid granulations.
What is the most common cause of congenital hydrocephalus?
Aqueductal stenosis –> leads to insufficient drainage of CSF.
What is aqueductal stenosis?
The cerebral aqueduct that connects the third and fourth ventricle is stenosed (narrowed).
This blocks the normal flow of CSF out of the third ventricle, causing CSF to build up in the lateral and third ventricles.
Where does CSF build up in aqueductal stenosis?
3rd ventricle & lateral ventricles
What can hydrocephalus be broadly divided into?
1) Obstructive (‘non-communicating’) hydrocephalus
2) Non-obstructive (‘communicating’) hydrocephalus
What is obstructive (‘non-communicating’) hydrocephalus?
Due to a structural pathology blocking the flow of CSF.
Dilatation of the ventricular system is seen superior to site of obstruction.
Give some causes of obstructive hydrocephalus
- tumours
- acute haemorrhage (e.g. SAH or intraventricular haemorrhage)
- developmental abnormalities (e.g. aqueduct stenosis).
What is non-obstructive hydrocephalus?
Due to an imbalance of CSF production and absorption.
Causes of non-obstructive hydrocephalus
1) an increased production of CSF (e.g. choroid plexus tumour - very rare
2) failure of reabsorption at the arachnoid granulations (e.g. meningitis or post-haemorrhagic) - more common
What is normal pressure hydrocephalus?
A unique form of non-obstructive hydrocephalus characterised by large ventricles but normal intracranial pressure.
What classic triad of symptoms is seen in normal pressure hydrocephalus?
1) dementia
2) urinary incontinence
3) disturbed gait
give 4 causes of congenital hydrocephalus
1) aqueductal stenosis
2) arachnoid cysts: can block the outflow of CSF if they are large enough
3) Arnold-Chiari malformation
4) chromosomal abnormalities and congenital malformations can cause obstruction to CSF drainage.
What is the Arnold-Chiari malformation?
Where the cerebellum herniates downwards through the foramen magnum, blocking the outflow of CSF
What causes an enlarged and rapidly increasing head circumference (occipito-frontal circumference) in babies with hydrocephalus?
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.
Presentation of congenital hydrocephalus?
1) Enlarged and rapidly increasing head circumference
2) Bulging anterior fontanelle
3) Poor feeding and vomiting
4) Poor tone
5) Sleepiness
6) If severe: failure of upward gaze (‘sunsetting’ eyes) due to compression of the superior colliculus of the midbrain
1st line imaging in hydrocephalus?
CT head
Investigations in hydrocephalus?
1) CT head
2) MRI head: may be used to investigate hydrocephalus in more detail
3) Lumbar puncture: both diagnostic and therapeutic (allows you to sample CSF, measure the opening pressure, and also to drain CSF to reduce the pressure)
What is the mainstay of treatment for hydrocephalus?
Ventriculoperitoneal (VP) shunt
What does a VP shunt involve?
This shunt drains CSF from the ventricles into another body cavity (usually the peritoneal cavity).
When should a LP not be done in hydrocephalus?
In obstructive hydrocephalus –> the difference of cranial and spinal pressures induced by the drainage of CSF will cause brain herniation.
Where is CSF diverted to with a ventriculoperitoneal shunt?
Peritoneal cavity
What management can be used in acute, severe hydrocephalus?
An external ventricular drain (EVD) - this is typically inserted into the right lateral ventricle and drains into a bag at the bedside
What are some potential complications of a VP shunt?
- infection
- blockage
- excessive drainage
- intraventricular haemorrhage
- outgrowing them (they typically need replacing around every 2 years as the child grows)
What is craniosynostosis?
Premature fusion of the skull sutures –> this results in abnormal head shapes and restriction to the growth of the brain.
Complications of craniosynostosis?
If untreated, can lead to raised ICP.
Resulting symptoms:
- developmental delay
- cognitive impairment
- vomiting
- irritability
- visual impairment
- neurological symptoms
- seizures
What is the main presenting feature in craniosynostosis?
An abnormal head shape depending, on the affected cranial suture.
Give the affected suture for the following head shapes in craniosynostosis
1) Bulging on one side of the forehead
2) Long and narrow from front to back
3) Pointy triangular forehead
4) Flattening on one side of the occiput
1) Saggital suture
2) Coronal suture
3) Metopic suture
4) Labdoid suture
1st line investigation in craniosynostosis?
1st line: Skull XR
2nd line: CT head with bone views is used to confirm the diagnosis or exclude it if there is doubt on the XR.
Management of craniosynostosis?
Mild cases may be monitored and followed up over time. More severe cases require surgery for surgical reconstruction of the skull.
What is plagiocephaly?
Abnormal head shape - flattening of one area of the baby’s head.
‘Parallelogram shaped head’
Why has the incidence of plagiocephaly increased over the past decade?
This may be due to the success of the ‘Back to Sleep’ campaign (to reduce the risk of sudden infant death syndrome).
What is brachycephaly?
Refers to flattening at the back of the head, resulting in a short head from back to front.
What causes plagiocephaly and brachycephaly?
Occur when a baby had a tendency to rest their head on a particular point, resulting in the skull bones and sutures moulding with gravity to create an abnormal head shape.
This is called positional plagiocephaly.
Why was the ‘back to sleep’ campaign introduced?
To reduce the risk of sudden infant death syndrome
What needs to be excluded in any baby with an abnormal head shape?
Exclude craniosynotosis with a thorough history and properly palpating the sutures.
Where there is doubt refer for specialist assessment and imaging.
Congenital muscular torticollis (CMT) is a condition that can result in an abnormal head shape.
How?
Congenital muscular torticollis (CMT) is a shortening of the sternocleidomastoid muscle on one side.
This may be the reason the child always rests on one side of their head.
Management –> physio
Mainstay of management of abnormal head shape in babies?
Reassurance is key. An abnormal head shape can cause a lot of parental anxiety. In the vast majority of cases the head shape will return to normal as the child grows.
What simple measures can be taken to encourage the baby to avoid resting on the flattened area?
1) Positioning them on the rounded side for sleep
2) Supervised tummy time
3) Using rolled towels or other props
4) Minimising time in pushchairs and car seats
What is muscular dystrophy the umbrella term for?
Genetic conditions that cause gradual weakening and wasting of muscles.
What is the main muscular dystrophy to know about?
Duchennes muscular dystrophy
What is Duchenne muscular dystrophy?
An x-linked disorder associated with progressive proximal muscle weakness in children.
How is Duchenne’s inherited?
X-linked recessive
Why are only males affected with Duchenne’s?
A female carrying a mutation in one gene, with a normal gene on the other X chromosome, is generally unaffected.
What gene is affected in Duchenne’s?
The gene encoding dystrophin on the X chromosome
What is dystrophin?
Dystrophin is part of a large membrane associated protein in muscle which connects the muscle membrane to actin, part of the muscle cytoskeleton.
This protein helps hold muscles together at the cellular level.
What is the average age of diagnosis of Duchenne’s?
4 years
Clinical features of Duchenne’s?
1) Proximal muscle weakness, of a proximal to distal pattern (usually wheelchair bound by the time they become a teenage)
2) Motor milestones may be delayed
3) Gait abnormalities (e.g. waddling gait) and frequent falls are common
4) Calf pseudohypertrophy
5) Gower’s sign
6) 30% of patients have intellectual impairment
What is Gower’s sign?
The child assumes the hands-and-knees position and then climbs to a stand by “walking” his hands progressively up his shins, knees, and thighs.
This indicates proximal muscle weakness –> because the muscles around the pelvis are not strong enough to get their upper body erect without the help of their arms.
What condition does Gower’s sign indicate?
Duchenne’s muscular dystrophy
What investigation serves as a good screening test for Duchenne’s?
Creatinine kinase (CK) - nearly always raised.
What is used to confirm the diagnosis of Duchenne’s?
Genetic testing
What medication is used in the management of Duchenne’s?
oral prednisolone - to improve muscle function
Life expectancy of Duchenne’s?
25-35 years with good management of the cardiac and respiratory complications.
What is a key cardiac complication of Duchenne’s?
Dilated cardiomyopathy.
What investigation is used to assess for dilated cardiomyopathy in Duchenne’s?
Annual echo
What is the key respiratory complication of Duchenne’s?
respiratory failure secondary to muscular weakness
What are some complications seen 2ary to longterm corticosteroid use in Duchenne’s?
- osteoporosis
- impaired glucose tolerance
- obesity
- Addisonian crisis triggered by suddenly stopping steroids or intercurrent illness
Name 7 types of muscular dystrophy
1) Duchennes muscular dystrophy
2) Beckers muscular dystrophy
3) Myotonic dystrophy
4) Facioscapulohumeral muscular dystrophy
5) Oculopharyngeal muscular dystrophy
6) Limb-girdle muscular dystrophy
7) Emery-Dreifuss muscular dystrophy
What is Beckers muscular dystrophy?
A ‘less severe’ version of Duchenne’s.
I.e. the dystrophin gene is less severely affected and maintains some of its function
When does myotonic dystrophy typically present?
adulthood
What are some typical features of myotonic dystrophy?
1) progressive muscle weakness
2) prolonged muscle contractions
3) cataracts
4) cardiac arrhythmias
What is the hallmark feature of myotonic dystrophy?
Delayed muscle relaxation following voluntary contraction or percussion (myotonia).
I.e. prolonged muscle contraction
This may present in exams with a patient that is unable to let go after shaking someones hand, or unable to release their grip on a doorknob after opening a door.
How does facioscapulohumeral muscular dystrophy typically present?
Usually presents in childhood with weakness around the face, progressing to the shoulders and arms.
A classic initial symptom is sleeping with their eyes slightly open and weakness in pursing their lips.
They are unable to blow their cheeks out without air leaking from their mouth.
How does oculopharyngeal muscular dystrophy usually present?
In late adulthood with weakness of the ocular muscles (around the eyes) and pharynx (around the throat.
It typically presents with bilateral ptosis, restricted eye movement and swallowing problems
What is spinal muscular atrophy?
A rare autosomal recessive disorder that causes a progressive loss of motor neurones, leading to progressive muscular weakness.
What does spinal muscular atrophy affect?
The lower motor neurones in the spinal cord.
What signs are present in spinal muscular atrophy?
LMN signs:
- fasciculations
- reduced muscle bulk
- reduced tone
- reduced power
- reduced/absent reflexes
What are the 4 categories of spinal muscular atrophy?
SMA type 1 to 4
These are numbered from most to least severe
What is the most common type of spinal muscular atrophy?
SMA type 2
Describe SMA type 1
Has an onset in the first few months of life, usually progressing to death within 2 years.
When does SMA type 2 present?
Has an onset within the first 18 months.
Prognosis of SMA type 2?
Most never walk, but survive into adulthood
Onset of SMA types 1 to 4?
1: onset in first few months of life
2: onset within first 18 months
3: onset AFTER the first year of life
4: onset in the 20s
Prognosis of SMA type 1 to 4?
1: Usually progressing to death within 2 years
2: Most never walk, but survive into adulthood
3: Most walk without support, but subsequently loose that ability. Respiratory muscles are less affected and life expectancy is close to normal.
4: Most will retain the ability to walk short distances but require a wheelchair for mobility. Everyday tasks can lead to significant fatigue. Respiratory muscles and life expectancy are not affected.
Management of spinal muscular atrophy?
Management is supportive and involves the MDT.
Physiotherapy can be helpful in maximising strength in the muscles and retaining respiratory function. Splints, braces and wheelchairs can be used to maximise function.
Respiratory support with non-invasive ventilation may be required to prevent hypoventilation and respiratory failure, particularly during sleep.
PEG feeding may be required when a weak swallow makes swallowing unsafe.
What is the role of dystrophin?
Stabilises the muscle cell membrane
Why does DMD cause dilated cardiomyopathy?
As dystrophin expressed in heart
What causes calf pseudohypertrophy in DMD?
Calves are enlarged from fat and fibrosis NOT muscle bulk increase
