Posts about neurology from 2 of our recent medical students

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Posted by Ilya Grinberg:

Last week I participated in the MDA clinic and there was one patient who really stuck out in my mind. He was a 17 year old male who had Duchenne Muscular Dystrophy. He was completely wheelchair-bound and could barely move any of his extremities. This obviously meant that he was completely reliant on people to take care of him and that he could not participate in the day to day activities that a normal person could. He was also starting to have breathing difficulty and probably would need to start therapy on a ventilator soon too.

DMD is an x-linked recessive disorder that affects boys from an early age. It affects 1 out of 3600 boys so it is not too uncommon. The disease is due to a mutation of the structural protein Dystrophin which is normally found in all muscles. The protein is found on the X chromosome which explains why it is an X-linked disease. Patients are usually born normally but will start gradually developing symptoms during the first few years of life. The first observations are usually progressive muscle weakness in proximal muscles in addition to muscle atrophy. One of the key clinical signs in DMD is calf psuedohypertrophy which occurs due to fibrosis of the necrotic muscle tissue. Another common finding that presents early on is Gower’s sign, where the patient uses his arms to stand up due to weakness in the proximal leg muscles.

Click here to find out more about DMD.

 

Posted by John Soliman:

What is Neurology one may ask? Prior to and during medical school I feel like the exposure to the study of neurology was very limited. Interaction between neurological patients and medical professions was far and few between. I have had little encounters with the realm that lies ahead. Prior to starting the clerkship I was very intimidated due to my lack of knowledge and ignorance. I can say jokingly I barely knew how to spell Neurology. Even the basics of neurology such as anatomy was daunting usually getting hung up on learning one part or area as seen in this video. I have to say I had something in common with Pinky.

After the 4 weeks of neurology I have realized that neurology covers a broad realm of knowledge and information on the central and peripheral nervous system.

During my clerkship I was lucky enough to be exposed to many patients encountering a lot of this medical conditions and problems. I was able to identify and correlate symptoms with disease states and vice versa.

The most memorable experience was the MDA clinic. I was able to meet and was integrated into the care of a lot of the Myotonic dystrophy patients. I was able to see hear their day to day life experience, talk to their care givers and be able to help with their care. After seeing patients like this it really brought “problems” Into perspective. The amazing thing was the broad range of how these medical conditions affect each individual differently.

I had the opportunity to see two brothers who are both affected with Myotonic Dystrophy. One brother can walk, talk and act normal with minimal weakness while the other was wheel chair bound. Talking to them brought home how a muscular dystrophy can affect the lives of affected individuals. Myotonic dystrophy is an autosomal dominant genetic process which means it can affect 50% of the carriers offspring. This may affect a family’s decision on having kids both mentally and psychologically. In this specific case, one of the brothers and his wife decided to adopt children due to the high risk of having a child with myotonic dystrophy. Dealing with something like this is a full time job on its own so it can be draining mentally, physically and financially on families.

Overall the experience has been great as I have gotten to see patients with medical conditions that I may not be able to see again. This clerkship has been knowledgeable and I has encountered a broad real of neurology that I never had experienced in the past.

Click here to find out more about Myotonic Dystrophy.

Click here to find out more about MDA Clinic at Monmouth.

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Gene therapy trial for Duchenne Muscular Dystrophy

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Duchenne and Becker muscular dystrophy are both caused by mutations in the same dystrophin gene.

How it this possible?

Well, the genetic code which is translated to from proteins “talks” in words made of three letters (base pairs).

dmd dna

A gene mutation that deletes only one or two base pairs, or worse still signals the end of the word (known a “premature stop codon”) will result it a very abnormal dysfunctional gene product, leading to complete deficiency of functioning dystrophin, and the more severe Duchenne Muscular Dystrophy.

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Normal muscle bx (a) vs Duchenne muscular dystrophy (b) with complete absence of dystrophin (d)

However a gene mutation (deletion) that removes base pairs in a multiples of three is called an in-frame mutation, and causes a (sometimes only minor) qualitative change in the dystrophin protein, leading to the milder Becker’s muscular dystrophy.

Ataluren (also known as PTC124) is a small molecule designed to overcome premature stop codons.

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Put simply, the idea is that it might convert some Duchenne boys in to a milder form (more like Becker’s) of muscular dystrophy by allowing them to produce some more normal dystrophin.

The drug can only help boys affected with premature stop codons confirmed by DNA testing.

The drug is currently undergoing Phase III trialsClick here for more information.

Duchenne Muscular Dystrophy

Posted by Elliot Dubowitch from Drexel University College of Medicine Class of 2014

Duchenne muscular dystrophy (DMD) is one of the four main groups  of muscular dystrophy, a muscle disorder that affects and weakens the musculoskeletal system.

Muscular dystrophies are genetically inherited and progressive.

DMD is inherited in an x-linked manner.  This means that the mother, who is unaffected, is a carrier for the disease and has a 50% chance of passing it on to her male children.

The disease is caused by a deficiency in the Dystrophin protein, a complex that anchors the muscle to surrounding tissue.

dystrophin

This disease has a wide spectrum of symptom severity, depending on the type of genetic mutation, with Duchenne being very severe, and Becker’s muscular dystrophy being much more mild.

The symptoms in DMD are not usually present at birth.  As the child ages, however, they symptoms will gradually become worse and worse.  Most children are unable to walk by thirteen years of age and die in their twenties due to respiratory failure.

One of the earliest signs of DMD is called to as the “Gower Maneuver.”  Although not pathognomonic for DMD, this maneuver is a sign for proximal muscle weakness and is often correlated with DMD.  Below is a clip of a child performing to Gower’s maneuver to stand.  The patient must “walk” up his body using his hands from a sitting position due to weakness in his hip and thigh muscles.  Below is a video clip demonstrating this.

Another early sign is calf pseudohypertrophy.  Although the muscle looks bigger, it is not necessarily stronger, as the functional muscle is replaced by nonfunctional fibrous tissue.

Unfortunately, there is currently no cure for DMD.  However, there is symptomatic treatment available, such as respiratory support, cardiovascular monitoring and treatment and (if needed) surgery for scoliosis.

Steroids are the only current medication that has been shown to keep the boys walking longer.  A study was conducted in which one group of boys were given steroids daily, whereas the other group of boys were given steroids 10 days on and 10 days off.  The boys receiving daily steroids walked on average until the age of 14.5 year, while the boys receiving steroids intermittently walked to only 12 years of age.  The boys receiving continuous steroids also had more side effects including weight gain, mood swings, increase risk of infection, and other side effects of steroid usage.  If one is to consider steroid use, it is imperative to remember that it must be used at the time the child is still ambulating.  The boy will not regain lost function, however he may retain his current function longer.  In the future we hope that new drugs like VBP-15 will hopefully provide the benefits of corticosteroids without some of the side effects.

Genetic research is currently being done to hopefully find a cure for this disease.

Neuromuscular respiratory failure

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Each lung is composed of >300 million tiny membrane bound sacs of air sacs (alveoli) which if spread out would cover a piece of ground roughly the size of a tennis court.  The purpose of this giant membrane is to exchange oxygen from the air for carbon dioxide from the blood stream.

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If the lungs become congested (or filled with fluid) from infection (pneumonia) or heart failure, it becomes harder to extract oxygen from the air:

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Treatment includes adding extra oxygen to the air to make this process more efficient.

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However, gas exchange across the alveoli can only occur if fresh air is brought into the lungs, and stale air is moved out, a process known as ventilation.  The diaphragm and muscles of the chest wall act like a giant bellows to make this happen:

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These muscles can become weak in nerve or muscle diseases such as Guillain-Barré syndrome, polio, amyotrophic lateral sclerosis (ALS), Duchenne Muscular Dystrophy and myasthenia gravis.

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These patients are evaluated by pulmonary function testing, which will usually show a low forced vital capacity, low cough flow, and in advanced cases, elevated end-tidal carbon dioxide level.

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Patients with this type of ventilatory failure do not need extra oxygen, their lungs can extract oxygen from air normally, they need mechanical assistance moving air across their lungs:

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Early neuromuscular respiratory muscle weakness causes nocturnal hypoventilation.  This is because the weakened diaphragm is even more inefficient when laying supine in bed with the stomach contents pressing up on it.

Nocturnal hypoventilation presents with daytime sleepiness, early morning headaches, fatigue, and impaired cognition.

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Click here to take an on-line test, and find out how sleepy you are during the day.  If you score 10 or higher, you might have a problem!

Nocturnal hypoventilation is best treated using a non-invasive respirator at night, either with a face or nose mask:

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Other patients use a negative pressure respirator vest, or cuirass, which requires the patient to wear an upper body shell  attached to a pump which actively controls the respiratory cycle:

cuirass

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Neuromuscular respiratory failure also leads to an ineffective cough, which in turn predisposes patients to aspiration, retention of secretions, or pneumonia.  Affected patients need to learn to use the cough assist machine when they get a minor respiratory tract infection to help them clear their secretions and prevent pneumonia:

cough assist

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More severe neuromuscular ventilatory failure leads to rapid shallow breathing, accessory respiratory muscle use, thoracoabdominal paradox (inward motion of the abdomen during inspiration), and ultimately high blood levels of carbon dioxide.

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Thoracoabdominal paradox – Normal (upper) abdomen moves outward with inspiration (diaphragm contraction). NM weakness (lower) abdomen moves in when patient inspires using accessory muscles.

In these cases, respiratory support is needed day and night.

Some patients can continue to use non invasive respiratory support, sleeping with a face or nose mask, and using a mouth piece intermittently during the day:

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Others cannot tolerate noninvasive ventilation or have anatomic abnormalities that preclude fitting of noninvasive ventilators.  Some disease, such as advanced ALS and Duchenne muscular dystrophy, affect the upper airway muscles as well as the diaphragm, impairing swallowing and compromising airway protection from aspiration.  These patients can chose to be managed with invasive respiratory support using a tracheotomy and conventional ventilator.

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Click here and and here to find out more about the management of neuromuscular respiratory failure.

New study compares steroid regimens in boys with Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) affects 1 in 3,600 boys and is caused by a mutation in the dystrophin gene, resulting in progressive muscle weakness.

Affected male children are normal at birth, but develop signs of muscle weakness before age 6, usually first affecting the legs and pelvis, causing difficulty getting up from the floor or a sitting position, and difficulty climbing stairs. Untreated boys are usually wheelchair dependent by age 12.

Ongoing research is leading towards pre-symptomatic diagnosis of DMD, and there has been some progress in genetic therapy for affected boys identified in these early stages of the disease.

However, so far corticosteroid therapy is the only treatment that has been shown to increase muscle strength in boys already affected with symptoms of DMD.

Steroids can cause side effects, and there is wide variability whether doctors doctors prescribe prednisone or deflazacort, as well as the dosing, duration of steroid use or even whether steroids are prescribed at all.

A new study aims to answer some of these questions.

The study is looking to enroll boys aged 4-7 with genetically confirmed DMD who have not taken steroids before.

They will be included in the study for 3-5 years and receive either:
1. Prednisone 0.75mg/Kg/d, or
2. Prednisone 0.75mg/Kg/d 10days on then 10 days off, or
3. Deflazacort 0.9mg/Kg/d

They will need hospital visits every 3 months for the first 6 months, then every 6 months thereafter.

This study is available locally at Penn Sate Hershey Medical Center – parents or physicians of interested patients should contact Beth Stephens at 717-531 0003 extension 283395 or by email for more information.

Drooping eyelids (ptosis)

Ptosis can affect one or both eyes and results from weakness affecting the muscles that raise the eyelid.

L ptosis

Left sided ptosis

Ptosis can be congenital (you are born with it), or acquired (it develops during life).

Acquired ptosis can result from a variety of problems affecting the nerves, muscles, neuromuscular junction or tendons involved in elevating the eye lids.

Neurogenic ptosis is usually unilateral, and can be caused by a lesion affecting either the oculomotor nerve or the sympathetic nerve fibers to the eye (Horner’s syndrome).

When ptosis is caused by an oculomotor nerve lesion, there is  generally also some degree of eye movement abnormality (ophthalmoparesis).  Oculomotor nerve palsy can be caused by something as simple as diabetes, but if the nerve fibers to the pupil are involved (causing a dilated pupil in addition to the ptosis and ophthalmoparesis), that is very suggestive of a compressive lesion such as an aneurysm (see below) and warrants immediate evaluation.

R ptosis, occulomotor palsy (eye is deviated down and outwards), with a dilated pupil, caused by nerve compression from aneurysm (red arrow)

R ptosis, oculomotor palsy (eye is deviated down and outwards), with a dilated unreactive pupil, caused by nerve compression from aneurysm (red arrow)

Horner’s syndrome causes mild ptosis associated with a small pupil (miosis) sometimes associated with lack of sweating (anhidrosis) on the face, and can be caused by trauma to the carotid artery, lung tumors, or strokes.

L Horner's syndrome with mild ptosis and miosis

L Horner’s syndrome with mild ptosis and miosis

Myasthenia gravis is an autoimmune disease that affects the neuromuscular junction, and frequently presents with fatiguable ptosis often associated with double vision and limb weakness.   The ptosis will usually get worse when the patients is tired at the end of the day (diurnal variation):

Fatiguable ptosis in myasthenia gravis

Fatiguable ptosis in myasthenia gravis

The ptosis of myasthenia can be temporarily improved with an acetylcholinesterase inhibitor medication, such as an injection of edrophonium (Tensilon), and this can used a diagnostic test.

Ptosis can also be seen in certain muscle diseases, including oculopharyngeal muscular dystrophy, mitochondrial myopathy and myotonic dystrophy.

Bilateral ptosis in a patient with myotonic muscular dystrophy

Bilateral ptosis in a patient with myotonic muscular dystrophy

However, acquired ptosis is most commonly caused by dehiscence or disinsertion of the levator aponeurosis, causing a disconnection between the eye lid and the elevating muscles.

This usually occurs in elderly patients, but can sometimes affect younger contact lens users.

L ptosis from levator dehiscence - Note that when the eye is closed, the lid crease is fainter and further away from the lid margin in the left eye, compared to the right eye

L ptosis from levator dehiscence – Note that when the eye is closed, the lid crease is fainter and further away from the lid margin in the left eye, compared to the right eye

Patients who notice a drooping eyelid, unequal pupils, or double vision should consult with a neurologist in order to establish the correct diagnosis.

After that, treatment might include medical therapy for an underlying disorder (such as diabetes or myasthenia), surgery or even eye lid crutches:

Myasthenic patient with isolated L ptosis, demonstrating improvement with the eye lid "crutch"

Myasthenic patient with isolated L ptosis, demonstrating improvement with the eye lid “crutch”