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doi:10.1111/jpc.12871
SHORT CASE
Floppy baby Michael Fahey Department of Paediatric Neurology, Monash Medical Centre, and Department of Paediatrics, Monash University, Melboune, Victoria, Australia
The floppy baby is often a surrogate combined neurological/ developmental/ dysmorphic examination. As such, you will need to follow a system and remain mentally flexible. As for any short case, think about what is going on while you are doing it. The major challenge in this examination is to distinguish whether a child has a central cause of floppiness or a peripheral cause. By central causes, I mean essentially the brain and, to a lesser extent, the spinal cord. Peripheral causes include, disease of the: Motor neurone, Peripheral nerve Neuromuscular junction Muscle As a rule, most floppy babies have a central cause for their floppiness. As is the case throughout paediatrics, the examination will need to be adapted depending on the age of the child. Start by having a look at the baby. Is the baby appropriately grown and is the head obviously large or small? Ask for the growth parameters including the head circumference. Check for obvious things like a tracheostomy and whether or not the child has a feeding tube that may be a clue to significant weakness. While you collect your thoughts take the opportunity to look at the parents and see whether or not they appear affected. Look at the child’s body positioning. Do they have any obvious contractures, including abnormal positioning of the arms or club-feet? Are they dysmorphic? Remember that there are clear dysmorphic syndromes associated with weakness and hypotonia including Prader Willi, trisomy 21, Miller Dieker syndrome and others. Does the face have any particular shape? Is it obviously myopathic? An extremely hypotonic mouth with ‘tented’ lips will be consistent with either congenital myotonic dystrophy or one of the congenital myopathies (i.e. myotubular or nemaline). Check the posture: are the legs in a frog leg position? Inspect the position of the arms. Do you think they have any antigravity movement? A simple way of assessing for anti-gravity movement is to use the ‘scarf sign’. To do this, pull the arm across the body like a scarf. In a normal infant, the knees lift up and across, showing an element of proximal strength. In infants with weakness (usually from peripheral causes), the leg will not lift. Where there is a discrepancy between hypotonia and strength: that is the child is very hypotonic but on performing the scarf manoeuvre there is apparent hip strength, conditions like Prader Willi should be considered. Inspect the chest: a pectus might indicate chronic involvement of chest muscles. Correspondence: Dr Michael Fahey, Department of Paediatric Neurology, Monash Medical Centre, 246 Clayton Road, Clayton, Vic. 3168, Australia. Fax: +613 9594 6259; email: [email protected]
Next the child should be lifted up. Axial strength can be tested by pulling the supine child up and assessing whether they can support their head. If the child is able to transition from lying to sitting, it is worth observing how they do this. In severe axial weakness, as might occur in spinal muscular atrophy type 2 (SMA 2), they may use sort of a seated Gower manoeuvre. Assess the child in ventral suspension; if they have a paradoxical truncal hypertonia, a central cause is suggested. At the same time, check if there are any signs on the back suggesting a spinal lesion. Following this, suspend them vertically and look for ‘slip through’ that would imply proximal upper limb weakness. During these manoeuvres, assess the alertness of the child. While you examined them, were they alert and interactive? If not, a central cause is more likely. Check in the mouth gently for fasciculations of the tongue. Observe the limbs for muscle bulk and contractures. Check for reflexes and plantar responses. Are there are any scars on the legs (usually over the vastus lateralis) that might indicate that a muscle biopsy has been undertaken? Check for organomegaly that may be associated with a metabolic cause. Brain and central causes tend to be associated with decreased alertness, increased reflexes and syndromic features. Spinal cord causes have a motor level below which the movements are decreased with increased reflexes in the same area. Sometimes scars are evident. Children whose floppiness is caused by lesions at the level of the motor neurone have normal alertness, absent reflexes throughout and fasciculations, particularly in the tongue. If the changes are worse more distally compared with proximally (length dependent), peripheral nerve involvement is implied and with decreased reflexes. Congenital disorders at the level of the neuromuscular junction are rare; they fluctuate and classically have facial involvement and arthrogryposis. Disorders of muscle tend to affect the proximal movements more or cause global weakness and are associated with facial weakness and possibly abnormal extra-ocular movements. Reflexes are decreased, and there may be contractures. In an older child see how they stand and look for signs of scoliosis or lordosis. When walking, look for signs of proximal versus distal strength and ask them to do a Gower manoeuvre. Ask them to run and look for symmetry and whether you can determine where their weakness might be. Do not forget to check the legs (usually vastus lateralis) for a muscle biopsy scar. Ask them to raise their hands above their head and look for use of accessory muscles or scapular winging. If you are suspicious of scapular winging, a further way to assess this is to get them into a wheelbarrow position and have a look at their back. If you are suspicious of a certain diagnosis, state this and ask the examiners if you should proceed to assess the child for associated features. In terms of how to proceed, a few general things
Journal of Paediatrics and Child Health 51 (2015) 355–356 © 2015 The Author Journal of Paediatrics and Child Health © 2015 Paediatrics and Child Health Division (Royal Australasian College of Physicians).
355
Floppy baby
M Fahey
can be useful in most cases of low tone: for example, obtaining a family history, examining the parents, measuring the serum creatine kinase, a brain magnetic resonance imaging (MRI) scan and performing nerve conduction studies or a muscle biopsy. When summarising, try to synthesise and interpret your findings. For example, ‘I was asked to examine Rupert, a two year old boy with weakness. He showed signs of a central cause for this. He is not as alert as I would expect a two year old boy to be and he has a dysmorphic face and is microcephalic. A syndrome may cause this however at this time, I am unable to nominate one. His limbs are weak but paradoxically hyperreflexic with upgoing plantar reflexes. My investigations would include an MRI brain scan and a DNA microarray test’.
Or: ‘I was asked to examine Kate a six-month-old girl with hypotonia. She has evidence of a peripheral cause and I am particularly suspicious of spinal muscular atrophy type 1. The reason is that she has significant, diffuse muscle weakness which contrasts with her alert face. She has absent reflexes throughout and has tongue fasciculations. This suggests that the lesion is in the anterior horn cells. Other less likely diseases of the anterior horn cell would be spinal muscular atrophy type 2, secondary to poliomyelitis or non-polio enterovirus infection, but these last two normally give patchy flaccid paralysis. My primary investigation would be a spinal muscular atrophy gene probe looking for characteristic changes within the spinal muscular atrophy genes’.
Cows by Madelyn Chaney (11) from Operation Art 2014.
356
Journal of Paediatrics and Child Health 51 (2015) 355–356 © 2015 The Author Journal of Paediatrics and Child Health © 2015 Paediatrics and Child Health Division (Royal Australasian College of Physicians)
doi:10.1111/jpc.12871
SHORT CASE
Floppy baby Michael Fahey Department of Paediatric Neurology, Monash Medical Centre, and Department of Paediatrics, Monash University, Melboune, Victoria, Australia
The floppy baby is often a surrogate combined neurological/ developmental/ dysmorphic examination. As such, you will need to follow a system and remain mentally flexible. As for any short case, think about what is going on while you are doing it. The major challenge in this examination is to distinguish whether a child has a central cause of floppiness or a peripheral cause. By central causes, I mean essentially the brain and, to a lesser extent, the spinal cord. Peripheral causes include, disease of the: Motor neurone, Peripheral nerve Neuromuscular junction Muscle As a rule, most floppy babies have a central cause for their floppiness. As is the case throughout paediatrics, the examination will need to be adapted depending on the age of the child. Start by having a look at the baby. Is the baby appropriately grown and is the head obviously large or small? Ask for the growth parameters including the head circumference. Check for obvious things like a tracheostomy and whether or not the child has a feeding tube that may be a clue to significant weakness. While you collect your thoughts take the opportunity to look at the parents and see whether or not they appear affected. Look at the child’s body positioning. Do they have any obvious contractures, including abnormal positioning of the arms or club-feet? Are they dysmorphic? Remember that there are clear dysmorphic syndromes associated with weakness and hypotonia including Prader Willi, trisomy 21, Miller Dieker syndrome and others. Does the face have any particular shape? Is it obviously myopathic? An extremely hypotonic mouth with ‘tented’ lips will be consistent with either congenital myotonic dystrophy or one of the congenital myopathies (i.e. myotubular or nemaline). Check the posture: are the legs in a frog leg position? Inspect the position of the arms. Do you think they have any antigravity movement? A simple way of assessing for anti-gravity movement is to use the ‘scarf sign’. To do this, pull the arm across the body like a scarf. In a normal infant, the knees lift up and across, showing an element of proximal strength. In infants with weakness (usually from peripheral causes), the leg will not lift. Where there is a discrepancy between hypotonia and strength: that is the child is very hypotonic but on performing the scarf manoeuvre there is apparent hip strength, conditions like Prader Willi should be considered. Inspect the chest: a pectus might indicate chronic involvement of chest muscles. Correspondence: Dr Michael Fahey, Department of Paediatric Neurology, Monash Medical Centre, 246 Clayton Road, Clayton, Vic. 3168, Australia. Fax: +613 9594 6259; email: [email protected]
Next the child should be lifted up. Axial strength can be tested by pulling the supine child up and assessing whether they can support their head. If the child is able to transition from lying to sitting, it is worth observing how they do this. In severe axial weakness, as might occur in spinal muscular atrophy type 2 (SMA 2), they may use sort of a seated Gower manoeuvre. Assess the child in ventral suspension; if they have a paradoxical truncal hypertonia, a central cause is suggested. At the same time, check if there are any signs on the back suggesting a spinal lesion. Following this, suspend them vertically and look for ‘slip through’ that would imply proximal upper limb weakness. During these manoeuvres, assess the alertness of the child. While you examined them, were they alert and interactive? If not, a central cause is more likely. Check in the mouth gently for fasciculations of the tongue. Observe the limbs for muscle bulk and contractures. Check for reflexes and plantar responses. Are there are any scars on the legs (usually over the vastus lateralis) that might indicate that a muscle biopsy has been undertaken? Check for organomegaly that may be associated with a metabolic cause. Brain and central causes tend to be associated with decreased alertness, increased reflexes and syndromic features. Spinal cord causes have a motor level below which the movements are decreased with increased reflexes in the same area. Sometimes scars are evident. Children whose floppiness is caused by lesions at the level of the motor neurone have normal alertness, absent reflexes throughout and fasciculations, particularly in the tongue. If the changes are worse more distally compared with proximally (length dependent), peripheral nerve involvement is implied and with decreased reflexes. Congenital disorders at the level of the neuromuscular junction are rare; they fluctuate and classically have facial involvement and arthrogryposis. Disorders of muscle tend to affect the proximal movements more or cause global weakness and are associated with facial weakness and possibly abnormal extra-ocular movements. Reflexes are decreased, and there may be contractures. In an older child see how they stand and look for signs of scoliosis or lordosis. When walking, look for signs of proximal versus distal strength and ask them to do a Gower manoeuvre. Ask them to run and look for symmetry and whether you can determine where their weakness might be. Do not forget to check the legs (usually vastus lateralis) for a muscle biopsy scar. Ask them to raise their hands above their head and look for use of accessory muscles or scapular winging. If you are suspicious of scapular winging, a further way to assess this is to get them into a wheelbarrow position and have a look at their back. If you are suspicious of a certain diagnosis, state this and ask the examiners if you should proceed to assess the child for associated features. In terms of how to proceed, a few general things
Journal of Paediatrics and Child Health 51 (2015) 355–356 © 2015 The Author Journal of Paediatrics and Child Health © 2015 Paediatrics and Child Health Division (Royal Australasian College of Physicians).
355
Floppy baby
M Fahey
can be useful in most cases of low tone: for example, obtaining a family history, examining the parents, measuring the serum creatine kinase, a brain magnetic resonance imaging (MRI) scan and performing nerve conduction studies or a muscle biopsy. When summarising, try to synthesise and interpret your findings. For example, ‘I was asked to examine Rupert, a two year old boy with weakness. He showed signs of a central cause for this. He is not as alert as I would expect a two year old boy to be and he has a dysmorphic face and is microcephalic. A syndrome may cause this however at this time, I am unable to nominate one. His limbs are weak but paradoxically hyperreflexic with upgoing plantar reflexes. My investigations would include an MRI brain scan and a DNA microarray test’.
Or: ‘I was asked to examine Kate a six-month-old girl with hypotonia. She has evidence of a peripheral cause and I am particularly suspicious of spinal muscular atrophy type 1. The reason is that she has significant, diffuse muscle weakness which contrasts with her alert face. She has absent reflexes throughout and has tongue fasciculations. This suggests that the lesion is in the anterior horn cells. Other less likely diseases of the anterior horn cell would be spinal muscular atrophy type 2, secondary to poliomyelitis or non-polio enterovirus infection, but these last two normally give patchy flaccid paralysis. My primary investigation would be a spinal muscular atrophy gene probe looking for characteristic changes within the spinal muscular atrophy genes’.
Cows by Madelyn Chaney (11) from Operation Art 2014.
356
Journal of Paediatrics and Child Health 51 (2015) 355–356 © 2015 The Author Journal of Paediatrics and Child Health © 2015 Paediatrics and Child Health Division (Royal Australasian College of Physicians)
