The most common bulbar complaints irrespective of SMA type are difficulties in biting, fatigue while chewing, choking, and a weak speaking voice. (Bulbar refers to the bulblike part of the brainstem, and weakness there can cause difficulties with talking, chewing, swallowing, and holding up the head.)
The study, “Bulbar Problems Self-Reported by Children and Adults with Spinal Muscular Atrophy” was published in the Journal of Neuromuscular Diseases.
SMA, a genetic disease characterized by the progressive loss of nerve cells that control muscle movement, called motor neurons, leads to muscle weakness and atrophy, among other symptoms. Disease course and symptom severity varies across patients mostly by disease type (SMA 1–4), which is based on age at onset and the achievement motor milestones, such as independent sitting and walking.
A few studies have reported problems in SMA patients related to bulbar functions. In some, patients have had trouble with biting, chewing, opening the mouth, and swallowing, all of which can compromise nutrition and bowel function. But available research into bulbar problems in SMA is “relatively small,” the study said, and does not cover “the full spectrum of SMA.”
A team led by researchers at University Medical Center Utrecht, in the Netherlands, evaluated the prevalence of self-reported bulbar dysfunction (i.e., chewing, swallowing, and speech) in SMA patients.
The study enrolled a total of 118 patients and caregivers, ages 1 to 75, included in the Dutch SMA registry. Regarding patients, 11 had SMA type 1, 55 had SMA type 2, 26 had type 3a, and another 26 had type 3b or 4. Patients or their caregivers were asked to complete a questionnaire about feeding, swallowing, and speech.
Their answers revealed frequent complaints of problems with biting (34%), fatigue associated with chewing (44%), choking (56%), and difficulties speaking due to a weak voice (27%). Problems with the jaws, mastication (biting and chewing), and swallowing often appeared together. “This implies that when patients report jaw, mastication or swallowing problems, this may reflect a wider range or combination of bulbar problems,” the researchers wrote.
Mastication or swallowing problems were more frequently reported by or about patients with more severe forms of SMA, while jaw problems were equally common across different SMA types.
Results also indicated a degree of correlation between age, disease severity, and bulbar complaints. Among patients with SMA type 3a, those older than 30 tended to have more bulbar problems compared to younger people with this disease type.
To see if a link between existed bulbar activities and motor abilities, researchers analyzed the level of difficulties relative to patients’ physical skills (as measured by the Hammersmith scale) and their maximum ability to open the mouth.
The degree of physical disability poorly associated with jaw and chewing problems, and was only slightly related to swallowing difficulties. In contrast, physical disability was more strongly associated with speech problems.
In SMA type 2 patients, a poorer ability to open the mouth linked significantly, but weakly, with bulbar complaints.
“A significant proportion of SMA patients, including aging patients with milder variants, experience bulbar problems. This is important to note, as previous studies have primarily identified bulbar problems in younger and more severely affected patients,” the researchers said.
The team stressed that “fatigue associated with mastication and swallowing problems were frequently reported complaints,” and deserve further study.