Those at risk of being carriers of "SMN1" deletion, and thus at risk of having offspring affected by SMA, can undergo carrier analysis using a blood or saliva sample. The American College of Obstetricians and Gynecologists recommends all people thinking of becoming pregnant be tested to see if they are a carrier.

Routine prenatal or neonatal screening for SMA is controversial, because of the cost, and because of the severity of the disease. Some researchers have concluded that population screening for SMA is not cost-effective, at a cost of $5 million per case averted in the United States as of 2009. Others conclude that SMA meets the criteria for screening programs and relevant testing should be offered to all couples. The major argument for neonatal screening is that in SMA type I, there is a critical time period in which to initiate therapies to reduce loss of muscle function and proactive treatment in regards to nutrition.

In regards to the diagnosis of spinal and bulbar muscular atrophy, the "AR Xq12" gene is the focus. Many mutations are reported and identified as missense/nonsense, that can be identified with 99.9% accuracy. Test for this gene in the majority of affected patients yields the diagnosis.

While the presence of several symptoms may point towards a particular genetic disorder of the spinal muscular atrophy group, the actual disease can be established with full certainty only by genetic testing which detects the underlying genetic mutation.

Diagnostic procedures that may reveal muscular disorders include direct clinical observations. This usually starts with the observation of bulk, possible atrophy or loss of muscle tone. Neuromuscular disease can also be diagnosed by testing the levels of various chemicals and antigens in the blood, and using electrodiagnostic medicine tests including electromyography (measuring electrical activity in muscles) and nerve conduction studies.

In neuromuscular disease evaluation, it is important to perform musculoskeletal and neurologic examinations. Genetic testing is an important part of diagnosing inherited neuromuscular conditions.

Since December 2016, autosomal recessive proximal spinal muscular atrophy can be treated with nusinersen. No cure is known to any of the remaining disorders of the spinal muscular atrophies group. The main objective there is to improve quality of life which can be measured using specific questionnaires. Supportive therapies are widely employed for patients who often also require comprehensive medical care involving multiple disciplines, including pulmonology, neurology, orthopedic surgery, critical care, and clinical nutrition. Various forms of physiotherapy and occupational therapy are frequently able to slow down the pace of nerve degeneration and muscle wasting. Patients also benefit greatly from the use of assistive technology.

The importance of correctly recognizing progressive muscular atrophy as opposed to ALS is important for several reasons.

- 1) the prognosis is a little better. A recent study found the 5-year survival rate in PMA to be 33% (vs 20% in ALS) and the 10-year survival rate to be 12% (vs 6% in ALS).

- 2) Patients with PMA do not suffer from the cognitive change identified in certain groups of patients with MND.

- 3) Because PMA patients do not have UMN signs, they usually do not meet the "World Federation of Neurology El Escorial Research Criteria" for “Definite” or “Probable” ALS and so are ineligible to participate in the majority of clinical research trials such as drugs trials or brain scans.

- 4) Because of its rarity (even compared to ALS) and confusion about the condition, some insurance policies or local healthcare policies may not recognize PMA as being the life-changing illness that it is. In cases where being classified as being PMA rather than ALS is likely to restrict access to services, it may be preferable to be diagnosed as "slowly progressive ALS" or "lower motor neuron predominant" ALS.

An initial diagnosis of PMA could turn out to be slowly progressive ALS many years later, sometimes even decades after the initial diagnosis. The occurrence of upper motor neurone symptoms such as brisk reflexes, spasticity, or a Babinski sign would indicate a progression to ALS; the correct diagnosis is also occasionally made on autopsy.

A 2006 study followed 223 patients for a number of years. Of these, 15 died, with a median age of 65 years. The authors tentatively concluded that this is in line with a previously reported estimate of a shortened life expectancy of 10-15 years (12 in their data).

PMA is a diagnosis of exclusion, there is no specific test which can conclusively establish whether a patient has the condition. Instead, a number of other possibilities have to be ruled out, such as multifocal motor neuropathy or spinal muscular atrophy. Tests used in the diagnostic process include MRI, clinical examination, and EMG. EMG tests in patients who do have PMA usually show denervation (neurone death) in most affected body parts, and in some unaffected parts too.

It typically takes longer to be diagnosed with PMA than ALS, an average of 20 months for PMA vs 15 months in ALS/MND.

The diagnosis for DMSA1 is usually masked by a diagnosis for a respiratory disorder. In infants, DMSAI is usually the cause of acute respiratory insufficiency in the first 6 months of life. The respiratory distress should be confirmed as diaphragmatic palsy by fluoroscopy or by electromyography. Although the patient may have a variety of other symptoms the diaphragmatic palsy confirmed by fluoroscopy or other means is the main criteria for diagnosis. This is usually confirmed with genetic testing looking for mutations in the "IGHMBP2" gene.

The patient can be misdiagnosed if the respiratory distress is mistaken for a severe respiratory infection or DMSA1 can be mistaken for SMA1 because their symptoms are so similar but the genes which are affected are different. This is why genetic testing is necessary to confirm the diagnosis of DMSA.

Electrodiagnostic testing (also called electrophysiologic) includes nerve conduction studies which involves stimulating a peripheral motor or sensory nerve and recording the response, and needle electromyography, where a thin needle or pin-like electrode is inserted into the muscle tissue to look for abnormal electrical activity.

Electrodiagnostic testing can help distinguish myopathies from neuropathies, which can help determine the course of further work-up. Most of the electrodiagnostic abnormalities seen in myopathies are also seen in neuropathies (nerve disorders). Electrodiagnostic abnormalities common to myopathies and neuropathies include; abnormal spontaneous activity (e.g., fibrillations, positive sharp waves, etc.) on needle EMG and, small amplitudes of the motor responses compound muscle action potential, or CMAP during nerve conduction studies. Many neuropathies, however, cause abnormalities of sensory nerve studies, whereas myopathies involve only the muscle, with normal sensory nerves. The most important factor distinguishing a myopathy from a neuropathy on needle EMG is the careful analysis of the motor unit action potential (MUAP) size, shape, and recruitment pattern.

There is substantial overlap between the electrodiagnostic findings the various types of myopathy. Thus, electrodiagnostic testing can help distinguish neuropathy from myopathy, but is not effective at distinguishing which specific myopathy is present, here muscle biopsy and perhaps subsequent genetic testing are required.

In terms of treatment for neuromuscular diseases (NMD), "exercise" might be a way of managing them, as NMD individuals would gain muscle strength. In a study aimed at results of exercise, in muscular dystrophy and Charcot-Marie-Tooth disease, the later benefited while the former did not show benefit; therefore, it depends on the disease Other management routes for NMD should be based on medicinal and surgical procedures, again depending on the underlying cause.

Electrophysiological evidence of denervation with intact motor and sensory nerve conduction findings must be made by using nerve conduction studies, usually in conjunction with EMG. The presence of polyphasic potentials and fibrillation at rest are characteristic of congenital dSMA.

The following are useful in diagnosis:

- Nerve conduction studies (NCS), to test for denervation

- Electromyography (EMG), also to detect denervation

- X-ray, to look for bone abnormalities

- Magnetic resonance imaging (MRI)

- Skeletal muscle biopsy examination

- Serum creatine kinase (CK) level in blood, usually elevated in affected individuals

- Pulmonary function test

On examination of muscle biopsy material, the nuclear material is located predominantly in the center of the muscle cells, and is described as having any "myotubular" or "centronuclear" appearance. In terms of describing the muscle biopsy itself, "myotubular" or "centronuclear” are almost synonymous, and both terms point to the similar cellular-appearance among MTM and CNM. Thus, pathologists and treating physicians use those terms almost interchangeably, although researchers and clinicians are increasingly distinguishing between those phrases.

In general, a clinical myopathy and a muscle biopsy showing a centronuclear (nucleus in the center of the muscle cell) appearance would indicate a centronuclear myopathy (CNM). The most commonly diagnosed CNM is myotubular myopathy (MTM). However, muscle biopsy analysis alone cannot reliably distinguish myotubular myopathy from other forms of centronuclear myopathies, and thus genetic testing is required.

Diagnostic workup is often coordinated by a treating neurologist. In the United States, care is often coordinated through clinics affiliated with the Muscular Dystrophy Association.

MMA mostly occurs in males between the ages of 15 and 25. Onset and progression are slow. MMA is seen most frequently in Asia, particularly in Japan and India; it is much less common in North America.

The subtypes of congenital muscular dystrophy have been established through variations in multiple genes. It should be noted that phenotype, as well as, genotype classifications are used to establish the subtypes, in some literature.

One finds that congenital muscular dystrophies can be either autosomal dominant or autosomal recessive in terms of the inheritance pattern, though the latter is much more common

Individuals who suffer from congenital muscular dystrophy fall into one of the following "types":

For the diagnosis of congenital muscular dystrophy, the following tests/exams are done:

- Lab study (CK levels)

- MRI (of muscle, and/or brain)

- EMG

- Genetic testing

There is no cure for MMA. Treatment consists of muscle strengthening exercises and training in hand coordination. It has been proposed that the changes in this disease are from compression of the spinal cord in flexion due to forward shifting of the posterior dural sac. There have been treatments studies ranging from use of a cervical collar to anterior cervical fusion and posterior decompression.

DSMA1 is usually fatal in early childhood. The patient, normally a child, suffers a progressive degradation of the respiratory system until respiratory failure. There is no consensus on the life expectancy in DSMA1 despite a number of studies being conducted. A small number of patients survive past two years of age but they lack signs of diaphragmatic paralysis or their breathing is dependent on a ventilation system.

A CT scan can distinguish muscle tissue from other tissues and thereby estimate the amount of muscle tissue in the body.

Fast loss of muscle tissue (relative to normal turnover), can be approximated by the amount of urea in the urine. The equivalent nitrogen content (in gram) of urea (in mmol) can be estimated by the conversion factor 0.028 g/mmol. Furthermore, 1 gram of nitrogen is roughly equivalent to 6 gram of protein, and 1 gram of protein is roughly equivalent to 4 gram of muscle tissue. Subsequently, in situations such as muscle wasting, 1 mmol of excessive urea in the urine (as measured by urine volume in litres multiplied by urea concentration in mmol/l) roughly corresponds to a muscle loss of 0.67 gram.

Diagnosis of post-polio syndrome can be difficult, since the symptoms are hard to separate from complications due to the original poliomyelitis infection, and from the normal infirmities of aging. There is no laboratory test for post-polio syndrome, nor are there any other specific diagnostic criteria. Three important criteria are recognized, including: previous diagnosis of polio, long interval after recovery and the gradual onset of weakness.

In general, PPS is a diagnosis of exclusion whereby other possible causes of the symptoms are eliminated. Neurological examination aided by other laboratory studies can help to determine what component of a neuromuscular deficit occurred with polio and what components are new and to exclude all other possible diagnoses. Objective assessment of muscle strength in PPS patients may not be easy. Changes in muscle strength are determined in specific muscle groups using various muscle scales which quantify strength, such as the Medical Research Council (MRC) scale. Magnetic resonance imaging (MRI), neuroimaging, and electrophysiological studies, muscle biopsies, or spinal fluid analysis may also be useful in establishing a PPS diagnosis.

There are two tests that can provide a definite diagnosis of myelomalacia; magnetic resonance imaging (MRI), or myelography. Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to visualize the internal structure of the body used in the diagnosing of myelomalacia. Certain MRI findings can detect where bone density and matter has been lost in people with spinal cord injuries. Diffuse hyperintensity appreciated on T2-weighted imaging of the spinal cord can be an indication of the onset or progression of myelomalacia

Because different types of myopathies are caused by many different pathways, there is no single treatment for myopathy. Treatments range from treatment of the symptoms to very specific cause-targeting treatments. Drug therapy, physical therapy, bracing for support, surgery, and massage are all current treatments for a variety of myopathies.

The diagnosis of limb-girdle muscular dystrophy can be done via muscle biopsy, which will show the presence of muscular dystrophy, and genetic testing is used to determine which type of muscular dystrophy a patient has. Immunohistochemical dystrophin tests can indicate a decrease in dystrophin detected in sarcoglycanopathies. In terms of sarcoglycan deficiency there can be variance (if α-sarcoglycan and γ-sarcoglycan are not present then there's a mutation in LGMD2D).

The 2014 "Evidence-based guideline summary: Diagnosis and treatment of limb-girdle and distal dystrophies" indicates that individuals suspected of having the inherited disorder should have genetic testing. Other tests/analysis are:

- High CK levels(x10-150 times normal)

- MRI can indicate different types of LGMD.

- EMG can confirm the myopathic characteristic of the disease.

- Electrocardiography (cardiac arrhythmias in LGMD1B can occur)

Onset of first symptom has been reported between 1–12 years, with a mean age of onset at 8 years. Clinical course can be divided into early (< 6 yrs age, predominance of respiratory symptoms) and late course (6–20 years of age, predominance of motor symptoms on superior limbs). Progression to involve other cranial nerve muscles occurs over a period of months or years. In the Gomez review facial nerve was affected in all cases while hypoglossal nerve was involved in all except one case. Other cranial nerves involved were vagus, trigeminal, spinal accessory nerve, abducent, occulomotor and glossopharyngeal in this order. Corticospinal tract signs were found in 2 of the 14 patients.

The disease may progress to patient's death in a period as short as 9 months or may have a slow evolution or may show plateaus. Post mortem examination of cases have found depletion of nerve cells in the nuclei of cranial nerves. The histologic alterations found in patient with Fazio–Londe disease were identical to those seen in infantile-onset spinal muscular atrophy.

Strength may improve with administration of cholinesterase inhibitors.