Approach to hypotonia (newborn and infant): Clinical sciences

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Introduction0:00–0:25

Hypotonia or decreased muscle tone is characterized by poor movement and posture control or delayed motor skills. Newborns or infants with hypotonia are often described as floppy.
You can categorize hypotonia as conditions affecting the central or peripheral nervous system. If a pediatric patient presents with hypotonia, perform an ABCD E assessment to determine if they are stable or unstable.

Unstable Patient0:25–1:02

If unstable, stabilize the airway, breathing and circulation and consider intubation if necessary. Obtain IV access, consider giving IV fluids, begin continuous vital sign monitoring and provide supplemental oxygen if needed.
Finally consider a full sepsis workup and antibiotics for newborns. Since hypotonia might be related to sepsis when it comes to stable patients.

Stable Patient/Central Nervous System Causes1:02–2:48

Your next step is to obtain a focused history and physical examination. There are a few things you should look out for.
Generally, these patients present with motor delay. It's also important to determine if hypotonia was present at birth or developed progressively as this will be a clue to the cause.
Be sure to assess for clues of central nervous system, cns involvement like seizures, cognitive vision or hearing issues.
Next, assess if there is upper or lower motor neuron involvement. As a reminder, upper motor neuron lesions will present with spasticity and hyperreflexia.
While lower motor neuron lesions will present with hypotonia and reduced or absent reflexes. Finally ask about family history.
First, let's discuss central nervous system etiologies of hypotonia history might include developmental regression or seizures.
While the exam reveals reduced alertness, normal strength or hyperactive or normal reflexes as well as the presence of primitive reflexes.
Patients may have microcephaly or macrocephaly and their eyes might not track, they might display hand fisting or scissoring on vertical suspension.
With these findings, consider a central nervous system etiology. Obtain brain imaging like CT or MRI an eeg and a metabolic screen including ACM P and ammonia level.

IEMs2:48–3:25

Let's go over your findings starting with inborn errors of metabolism, affected newborns are often healthy at birth but develop hypotonia over the 1st 12 to 24 hours.
Physical exam reveals signs suggesting organ dysfunction like arrhythmias or hepatomegaly imaging and eeg are usually nonspecific and might be abnormal.
Labs commonly reveal hypoglycemia or hyperammonemia which suggests inborn errors of metabolism. Next, let's look at genetic syndromes.

Genetic Syndromes3:25–5:12

If you see syndromic or dysmorphic features with normal brain imaging eeg and metabolic screen, consider genetic syndrome.
Now, if physical exam findings include flattened, posterior occiput up, slanted palpebral fissures, epicanthal folds, flat, nasal bridge, protuberant tongue, excess, posterior nuchal skin and a single palmar crease.
Consider Down syndrome. Next, obtain genetic testing to confirm trisomy 21 and diagnose Down syndrome.
Here's a clinical pearl other trisomies associated with hypotonia include Trisomy 13 Patau syndrome and Trisomy 18 Edward syndrome.
On the flip side if your patient had early feeding problems, but later developed an insatiable appetite. And exam reveals micropenis and cryptorchidism or clitoral and labial hypoplasia.
Consider Prader Willi and obtain genetic testing. A deletion of 15 Q 11 Q 13 confirms the diagnosis.
Here's a clinical pearl Fragile X syndrome is a genetic condition that presents with hypotonia during infancy. However, these Children aren't usually diagnosed until three or four years of age.
When learning and developmental disabilities begin, affected individuals typically demonstrate characteristic phenotypic features such as a prominent forehead and jaw, large, low set ears and macroorchidism in biological males.
All right, let's look at functional or structural brain abnormalities. If you see abnormal MRI findings like signal intensity changes or reduced gyri, an abnormal eeg revealing seizure activity and a normal metabolic screen.

Brain Abnormalities5:12–6:51

Consider a brain abnormality. First up is hypoxic ischemic encephalopathy or hie which is caused by perinatal hypoxemia.
These infants usually had a difficult delivery and developed poor feeding and seizures. Physical exam revealing autonomic dysfunction like decreased heart rate with stimuli and brain MRI demonstrating signal intensity changes suggest hie.
Next up are brain malformations. Affected.
Patients typically have hypotonia but gradually develop hypertonia. Exam findings include cranial nerve abnormalities like impaired eye abduction, babinski sign, global delay and micro or macrocephaly.
Imaging confirms a structural brain malformation like lissencephaly where the cerebral cortex is smooth holoprosencephaly where the cerebral hemispheres are not fully separated.
And Joubert syndrome, in which the cerebellar vermis is absent or underdeveloped. In these cases, you can diagnose brain malformations.

Spinal Cord Abnormality6:51–7:27

Finally, let's go back to our imaging and discuss spinal cord abnormalities. These patients may have a history of breech delivery and the exam demonstrates a spinal cord level sensory or motor abnormality.
However, imaging eeg and metabolic screening are normal with these findings, consider a spinal cord abnormality and obtain a spine.
MRI the presence of abnormalities like myelodysplasia, syringomyelia, arteriovenous malformation, trauma or tumor confirms a spinal cord abnormality.
Now, let's take a step back and talk about peripheral nervous system etiologies of hypotonia on exam. These patients are alert and respond appropriately to their surroundings but exhibit profound weakness, hyporeflexia or aflexia and muscle atrophy.

Peripheral Nervous System Causes7:27–7:59

In this case, consider peripheral nervous system etiologies and obtain a serum creatinine kinase level and electromyography or emg let's discuss motor neuron diseases.

Motor Neuron Disease7:59–8:34

History might reveal motor delay and feeding difficulties while the physical exam shows tongue fasciculations, which is an important sign of spinal muscular atrophy or sma and intention tremor is usually normal or mildly elevated but E MG indicates pure motor disease.
In this case, consider sma a and obtain genetic analysis if it reveals an SMN one deletion, diagnose sma A. Next, let's discuss neuropathies.

Neuropathies8:34–10:03

If the patient's is normal. The emg shows sensory and motor abnormalities and abnormal sensation.
Consider neuropathies. First up is Guillain Barre syndrome.
These patients typically have a preceding gastrointestinal or respiratory illness. And exam reveals rapidly progressive ascending weakness with pain or decreased sensation in the extremities.
E MG shows slow conduction velocities and delayed distal latencies with sparing of the sural nerve, meaning the sensory nerve action potential or snap is normal.
With. These findings consider Guillain barre and obtain a CSF analysis, increased protein with normal wbcs known as Cyto albumin logic dissociation supports the diagnosis.
Next is Charcot Marie tooth disease. These patients usually have family members with similar symptoms and the exam demonstrates slowly progressive weakness, decreased sensation or pain in the extremities, hammertoe, peas, cavus and foot drop.
Here. Consider Charcot Marie tooth disease and obtain a genetic analysis.
A duplication in the PMP 22 gene confirms the diagnosis. Now, let's discuss disorders of the neuromuscular junction CK levels are typically normal and E MG shows a decremental response with low frequency repetitive nerve stimulation.

Neuromuscular Junction Disorders10:03–12:28

These findings should make you consider neuromuscular junction disorders. First, let's discuss infantile botulism caused by clostridium botulinum toxin.
Honey often contains sea botulinum spores. So avoid giving honey to infants under one year of age affected infants develop hypotonia, constipation, lethargy and poor feeding several days after ingesting honey, exam reveals head drop ptosis, weak cry, and smile dilated sluggish pupils and bilateral descending paralysis at this point.
Consider botulism which can progress quickly from diaphragmatic weakness to respiratory failure. So be ready for urgent intubation.
Next. Obtain a stool culture and direct toxin assay of stool serum or gastric contents.
If the culture is positive or a clostridium botulinum or the botulinum toxin is positive diagnose infantile botulism. Let's move on to myasthenia gravis.
Patients have fluctuating weakness, feeding difficulties and occasionally a maternal history of myasthenia exam. Findings of ptosis, external ophthalmol plesia and preserved reflexes should make you consider myasthenia gravis.
Next, obtain acetylcholinesterase inhibitor response, anti acetylcholine receptor antibody serology and genetic analysis.
If there's a response to acetylcholinesterase inhibitors, positive serology and genetic mutations within the Chrne gene diagnose myasthenia gravis.
Here's another clinical pearl neonatal myasthenia gravis is acquired from a mother with myasthenia gravis. When anti acetylcholine receptor antibodies cross the placenta, it's typically transient and resolves within weeks to months.
While congenital myasthenia gravis is an autosomal recessive autoimmune condition causing lifelong symptoms. Finally, let's discuss muscle diseases if levels are normal or elevated and E MG demonstrates myopathic results like reduced spike durations.

Muscle Disease12:28–15:53

Consider muscle diseases with normal CK results consider myopathies which are skeletal muscle disorders that generally don't progress over time, obtain a muscle biopsy.
And if you detect rodlike structures called nemaline bodies diagnose myopathy. Now, if CK is elevated, consider muscular dystrophy, a group of disorders associated with muscle deterioration and progressive weakness.
First up is congenital myotonic dystrophy. These patients have a history of polyhydramnios in utero and a difficult delivery and later developed feeding and breathing difficulties.
The patient's mother may have delayed relaxation of her grip exam. Findings include myopathic facies with an open downturned mouth, facial diplasia, atrophy of temporalis muscles, joint deformities and club feet.
In this case, consider congenital myotonic dystrophy and obtain genetic analysis if there's a trinucleotide repeat expansion in DM PK diagnose congenital myotonic dystrophy.
Let's move on to Duchenne muscular dystrophy. An excellent recessive disorder primarily affecting males.
These patients have poor head control, calf pseudohypertrophy and the gower sign a maneuver affected Children use to walk their hands up to their legs to stand up.
There are also markedly elevated CK levels, often greater than 10,000. Here consider Duchenne muscular dystrophy and obtain a genetic analysis.
DMD gene mutation confirms the diagnosis. Let's discuss congenital muscular dystrophy, which is a group of disorders causing muscle weakness and hypotonia at birth history includes polyhydramnios in utero feeding and breathing difficulties after birth and possibly seizures.
Exam demonstrates a weak cry, poor suck, decreased spontaneous extremity movement and sometimes contractures and hyperkeratosis.
Polaris. With these findings consider congenital muscular dystrophy and obtain a brain MRI muscle biopsy and genetic analysis.
If biopsy identifies abnormalities like dystrophic changes, diagnose congenital muscular dystrophy. Finally, let's discuss pompe disease.
A storage disease associated with a lysosomal glycogen build up causing muscle wasting and weakness. History includes feeding and breathing difficulties.
Newborn screening may reveal low acid alpha glucosidase levels. While exam findings include a palpable liver and an enlarged tongue.
In this case, consider pompe disease and order a chest X ray. If it demonstrates severe cardiomegaly, obtain a genetic analysis, the presence of a mutation of GAA confirms pompe disease.
All right. It's a quick recap for a newborn or infant with hypotonia history and exam findings help determine the etiology.

Review15:53–16:41

Brain imaging eeg and metabolic screening. Identify causes related to the central nervous system, including inborn errors of metabolism down syndrome or Prader Willi syndrome.
Hie and structural brain malformation and spinal cord abnormalities. CK levels and emg identify peripheral nervous system causes such as sma a Guillain Barre and Charcot Marie tooth, infantile botulism or myasthenia gravis or myopathies and muscular dystrophy.