This pattern of weakness predominantly involves the distal muscles of the upper or lower extremities (anterior or posterior compartment muscle groups)
B ) The involvement is usually, although not invariably, symmetric.
C ) Selective weakness and atrophy in distal extremity muscles is more commonly a feature of neuropathies and therefore, a careful sensory and reflex examination must always be performed in patients presenting with this phenotype
III - PATTERN 3 ( Proximal Arm/Distal Leg Weakness (Scapuloperoneal)
A ) This pattern of weakness affects the peri-scapular muscles of the proximal arm and the anterior compartment muscles of the distal lower extremity, or the so-called “scapuloperoneal” distribution.
B ) The scapular muscle weakness is usually characterized by scapular winging.
C ) Weakness can be very asymmetric.
D ) When this pattern is associated with facial weakness, it is highly suggestive of a diagnosis of facioscapulohumeral muscular dystrophy
1 Other hereditary myopathies that are associated with a scapuloperoneal distribution of weakness include acid maltase deficiency, congenital myopathies, Emery-Dreifuss dystrophy, LGMD 1B (laminopathies), LGMD 2A (calpain), and LGMD 2C-F (sarcoglycans), and scapuloperoneal dystrophy.
IV - Distal Arm/Proximal Leg Weakness
A ) This pattern is associated with distal arm weakness involving the distal forearm muscles (wrist and finger flexors) and proximal leg weakness involving the knee extensors (quadriceps).
B ) The facial muscles are typically spared and involvement of other muscles is extremely variable.
C ) In addition, the weakness is often asymmetric between the two sides, which is uncommon in most myopathies.
D ) This pattern is essentially pathognomonic for inclusion body myositis.
V - Pattern 5: Ptosis With or Without Ophthalmoparesis
A ) Myopathies presenting with predominant involvement of ocular and/or pharyngeal muscles represent a relatively limited group of disorders .
B ) The ocular involvement principally results in ptosis and ophthalmoparesis which usually, although not always, occurs without symptoms of diplopia.
C ) Facial weakness is not uncommon and extremity weakness is extremely variable, depending on the diagnosis.
D ) The combination of ptosis, ophthalmoparesis without diplopia, and dysphagia should suggest the diagnosis of oculopharyngeal dystrophy, especially if there is a positive family history and the onset is in middle-age or later.
E ) Ptosis and ophthalmoparesis without prominent pharyngeal involvement is a hallmark of many of the mitochondrial myopathies.
F ) Ptosis and facial weakness without ophthalmoparesis is a common feature of myotonic dystrophy and fascioscapulohumeral dystrophy.
G ) Ptosis has diurnal variation in ocular myasthenia gravis and is often associated with diplopia
VI - PATTERN 6 - Prominent Neck Extensor Weakness
A ) This pattern is characterized by severe weakness of the neck extensor muscles. The term “dropped head syndrome” has been used in this situation .
B ) Involvement of the neck flexors is variable. Extremity weakness is dependent on the diagnosis and may follow one of the previously outlined phenotypic patterns.
C ) For example, a patient with a limb-girdle pattern of weakness may also have significant neck extensor involvement.
D ) Isolated neck extension weakness represents a distinct muscle disorder called isolated neck extensor myopathy
E ) Prominent neck extensor weakness is also common in two other neuromuscular diseases: amyotrophic lateral sclerosis and myasthenia gravis.
VII - PATTERN 7 Bulbar Weakness
1 Bulbar weakness, i.e. tongue and pharyngeal weakness, is manifested by symptoms of dysarthria and dysphagia.
2 While a number of myopathies can have some bulbar involvement, the muscular dystrophy that has bulbar involvement as a primary manifestation is oculopharyngeal muscular dystrophy.
3 Limb girdle muscular dystrophy type 1A (myotilinopathy) can present with isolated bulbar weakness and the inflammatory myopathies may rarely present in this manner.
4 Neuromuscular junction disorders such as myasthenia gravis and Lambert-Eaton myasthenic syndrome also frequently have bulbar symptoms and signs. This pattern is considered an “overlap” pattern with amyotrophic lateral sclerosis and other motor neuron disorders which can have significant bulbar involvement.
VIII - Pattern 8: Episodic Pain, Weakness and Myoglobinuria
1 This is the pattern characterized by a history of episodic pain, weakness, and myoglobinuria and may be related to a variety of conditions, many of which are not due to an underlying muscle disorder
2 When these symptoms are triggered by exercise, a metabolic myopathy is most likely.
3 However, a number of patients may develop myoglobuinuria because they are inactive individuals who are suddenly required to do an overwhelming amount of exercise, i.e. the “couch potato” syndrome.
Eg - 1 Related to exercise
“Couch Potato” syndrome
Glycogenoses (McArdle’s, etc.)
Lipid disorders (CPT deficiency)
2 Not related to exercise
Central non-neuromuscular causes:
Neuroleptic malignant syndrome
Status epilepticus
Drugs/toxins
Malignant hyperthermia
Polymyositis/Dermatomyositis (rarely)
Viral/bacterial infections
IX - Pattern 9: Episodic Weakness Delayed or Unrelated to Exercise
A ) This pattern applies to the disorders of periodic paralysis – both the genetic autosomal dominant channelopathies and the secondary periodic paralyses, such as those due to thyrotoxicosis.
B ) Also, for completeness sake, it is reasonable to include the neuromuscular junction disorders in this pattern.
C ) In all of these conditions, the weakness can occur during or after exercise, or often the weakness is unrelated to physical exertion.
D ) eg - Periodic paralysis
1 Ca++ channelopathies (hypokalemic)
2 Na++ channelopathies (hyperkalemic)
3 Andersen-Tawil syndrome
4 Secondary PP (thyrotoxicosis)
X - Pattern 10: Stiffness and Decreased Ability to Relax
1 This pattern includes all of the disorders that produce myotonia and paramyotonia and includes the hereditary disorders involving sodium and chloride channelopathies , as well as myotonic dystrophy types 1 and 2
2 Both myotonic dystrophies usually have fixed muscle weakness as well, with predominantly distal weakness in myotonic dystrophy type 1 and proximal weakness in myotonic dystrophy type 2.
3 The autosomal recessive form of chloride channelopathies, Becker’s disease, also has fixed proximal weakness.
4 In addition, other less common disorders that fit this pattern include Brody’s disease, neuromyotonia, and the central nervous system disorder, stiff-person syndrome