A case of neonatal essential tongue tremor diagnosed due to poor feeding

Abstract

We encountered a case of a neonate diagnosed with essential tongue tremor due to involuntary movements of the tongue and poor oral feeding immediately after birth. Reports of pediatric-onset essential tongue tremor, particularly neonatal-onset, are extremely rare. Neonatal-onset essential tongue tremor can result in feeding difficulties and poor weight gain, potentially affecting subsequent growth and development. Given the importance of early diagnosis and medical intervention, we report our case. A boy born at 40 weeks and 5 days of gestation, weighing 3252 g, normal delivery with an Apgar Score of 8/9. He exhibited poor feeding and tongue tremor since birth. A thorough examination was performed to differentiate involuntary tongue movements. Videofluoroscopic examination of swallowing showed stagnation of contrast medium in the oral cavity, suggesting that it was due to poor tongue movement. Based on clinical findings and various exclusion diagnoses, a diagnosis of essential tongue tremor was made. Primidone, a barbiturate anticonvulsant drug, was started with a therapeutic diagnosis. Treatment resulted in marked improvement in feeding ability, and the primidone was tapered off and discontinued without any side effects after weaning was introduced. We plan to carefully follow up on growth and developmental assessment (especially language development) and continue to provide support to patients and their families.

Introduction

Essential Tremor (ET) is characterized by involuntary rhythmic shaking at a frequency of 4 to 12 Hz. The hallmark symptom of ET is a postural or kinetic tremor, most commonly involving the upper limbs, which typically becomes apparent during actions. ¹

Tongue tremor is also associated with ET, but it is extremely rare as a first symptom. ²

Prevalence ranges from 40 to 400 per 10,000 persons due to regional differences and consultation rates. ¹ Reports in childhood, especially the neonatal period, are even more limited. ³

The authors report a case of a neonate with essential tongue tremor who presented with tongue tremor and poor oral feeding immediately after birth.

Case presentation (patient information)

A boy born at 40 weeks and 5 days of gestation, weighing 3252 g(−0.18SD), normal delivery with an Apgar Score of 8/9. There were no neurological or metabolic diseases in the family history. There were no special notes in the mother’s medication history. He was referred and admitted to the hospital at age 5 for a thorough examination. Weight at admission was –8.9% of birth weight (2986 g), oral intake was poor, and approximately 90% required tube feeding.

Differential diagnosis

There was no unusual facial appearance or deformity, and muscle tone and reflexes were normal. An oral examination focusing on the tongue was performed. There was no deviation of the tongue, the tremor was bilaterally symmetrical, and tongue protrusion was possible. Tongue anatomical abnormalities and Ankyloglossia, Submucous cleft palate were ruled out. Laryngoscopic examination was also conducted, and no velopharyngeal insufficiency or vocal cord paralysis was observed.

The patient was found to have a tremor (a rhythmic involuntary movement) of approximately 4 Hz in the tongue, which was enhanced during voluntary movements such as sucking and tongue protrusion, and was judged to be exercise-induced tremor (videos 1, 2).

Based on the results of the medical interview, drug-induced causes were ruled out. Blood tests showed no electrolyte abnormalities and hyperthyroidism, elevated enzymes, or blood glucose abnormalities. Neonatal mass screening tests (congenital metabolic abnormalities, spinal muscular atrophy) were also normal. No tongue fasciculations were observed, and no abnormalities were found in the head MRI and electroencephalogram tests. Based on the above, congenital metabolic, endocrine, and neurological disorders were ruled out.

Videofluoroscopic examination of swallowing showed impaired pharyngeal transfer of contrast medium due to impaired tongue movement, but swallowing movements after the pharynx were normal (Figure 1).

Figure 1.

Videofluoroscopic examination of swallowing.

Based on the clinical features and the diagnosis of exclusion, essential tongue tremor was most suspected.^4–6

Treatment

Considering the baby’s poor feeding associated with tongue tremor, we tried using a cleft palate nipple and a weak sucking nipple, but no obvious improvement was obtained. With the combination of nutrition via NG tube, weight gain progressed well at around 30 g/day after admission to our hospital. Based on past literature, we started primidone at day 28 at an initial dose (0.125 g/day) for the purpose of diagnostic treatment for ET. ⁷

An obvious increase in oral intake was observed, but the dose was increased because the tremor remained. The dose was tapered and temporarily discontinued because the blood concentration exceeded the optimal range (5–12 µg/mL) at day 33. However, because of a marked decrease in feeding volume, the drug was restarted at the initial dose and maintained. After day 51, oral feeding stabilized, the gastric tube was removed, and the patient was discharged at day 69 (Figure 2). Tongue tremor remained at discharge (video 3).

Figure 2.

Post-hospitalization progress (oral feeding volume and feeding rate).

Discussion

Since feeding requires the generation of negative pressure in the oral cavity and coordinated movement of the tongue, tongue tremor was thought to be a contributing factor to the feeding disorder in this case.

ET is diagnosed primarily based on clinical diagnosis (through medical interviews and physical examinations) and exclusionary diagnosis. ^4–6

Primidone and propranolol are first-line therapies for ET and sole medications for treating ET with the level A recommendations according to the latest guidelines of the American Academy of Neurology. ⁸ In this case, we could not be completely ruled out because neonatal seizures may not be captured by EEG abnormalities, and primidone was selected as the therapeutic diagnosis.

Primidone is a barbiturate antiepileptic drug that is metabolized to phenobarbital and phenylethylmalonamide (PEMA). ⁹ That is thought to exert its anti-tremor effect by modulating cortical GABA circuits, and numerous clinical trials have reported its efficacy in adult cases of ET.^10,11

After starting primidone, there was a clear improvement in symptoms, and a correlation with recurrence was observed, leading to a diagnosis of ET.

Significance and clinical contribution of this case

Previously reported literature did not mention cases in newborns. Tongue tremors in the neonatal period can cause poor feeding and poor weight gain, affecting growth and development, so early diagnosis and appropriate treatment are important.

While there have been reports of cases where tremors were alleviated with drug therapy, there have been no previous reports of cases like this one, where tremors persisted but adverse events such as poor feeding improved.

The rarity of the age of onset and clinical course, including the long-term growth and development of this case, contributes to neonatal medicine.

Limitations of this case and future challenges

The improvement in oral intake is thought to be due to the primidone,^12–14 but the influence of natural growth cannot be ruled out.

Effects on cognitive function and bone metabolism have been reported with long-term use. ¹⁵ In this case, the drug administration period was not prolonged, and the condition progressed without the onset of side effects. However, when symptoms flare up, it is necessary to carefully evaluate the risks and benefits of drug administration (including consideration of propranolol).

In neonatal cases, onset occurs before oral intake and language acquisition, compared to adult cases, posing a higher risk of affecting future growth and development. Follow-up using the Key Month developmental assessment is necessary, and support for the child and family should be considered to enable early intervention in the event of additional symptoms other than tongue tremor or complications associated with tremor.

Conclusion

We have experienced a neonatal case of ET of the tongue who presented with tongue tremor as the initial symptom and poor oral feeding.

The diagnosis was made based on exclusion and response to treatment, and a clear improvement in oral feeding rate was achieved with primidone. Although the influence of natural growth cannot be ruled out, tremors remain. It is important to carefully follow up growth and developmental assessment and continue to provide support to the patient and their family.