Drop episodes in Coffin-Lowry syndrome: exaggerated startle responses treated with clonazepam

Central Hypersomnia

Sleepiness is not uncommon in the pediatric population. Although the etiology can be multifactorial, sleepiness due to increased sleep drive, also called central hypersomnia, is a common cause. The third edition of the International Classification of Sleep Disorders updated the diagnostic criteria for several of the central disorders of hypersomnolence, most notably narcolepsy. Although the International Classification Of Sleep Disorders-3 is not specific to pediatric patients, the peak incidence for many of the included disorders occurs during childhood or adolescence. As a result, recognition of these lifelong and potentially debilitating disorders is imperative for providers who evaluate pediatric patients. This review provides an update on recent advances in the field and highlights some of the diagnostic dilemmas, unique clinical features, and variable presentations associated with central disorders of hypersomnolence within the pediatric population.

Stimulus-induced myoclonus treated effectively with clonazepam in genetically confirmed Coffin-Lowry syndrome

Purpose

Coffin–Lowry syndrome (CLS) is a rare X-linked semidominant syndromic genetic disorder that is characterized by typical facial and radiologic findings, psychomotor and growth retardation, and various skeletal anomalies. A distinctive paroxysmal disorder called stimulus-bound myoclonus is clinically heterogeneous and is generally characterized by a sudden loss of muscle tone that is regained within a few seconds and is induced by sudden auditory or tactile stimulus. As the pathophysiology of stimulus-induced drop episodes (SIDEs) is not well understood, there is no definite therapy for those episodes.

Methods

We report a 15-year-old female with stimulus-induced drop episodes occurring many times a day that resulted in failure to perform her daily activities. Because her SIDEs were misdiagnosed as atonic seizures, she was treated with several antiepileptic drugs, including valproic acid, levetiracetam, lamotrigine, primidone, carbamazepine, and clobazam.

Results

We realized that her clinical and radiological findings, together with SIDEs, are compatible with Coffin–Lowry syndrome. All of her medications were discontinued following the diagnosis of SIDE, and she was started on clonazepam. After treatment, she became more independent and was able to perform her daily activities. Subsequently, her episodes decreased from 3 times a day to 1–2 times a month. Sodium oxybate and fluoxetine were added to the treatment protocol without remarkable improvement. Her genetic analysis revealed a heterozygous variation of CLS.

Conclusion

We conclude that SIDE should be included in a differential diagnosis of epileptic seizures in patients with CLS and that clonazepam is an effective choice in the treatment of SIDEs.

Transient loss of consciousness and syncope

Syncope describes a sudden and brief transient loss of consciousness (TLOC) with postural failure due to cerebral global hypoperfusion. The term TLOC is used when the cause is either unrelated to cerebral hypoperfusion or is unknown. The most common causes of syncopal TLOC include: (1) cardiogenic syncope (cardiac arrhythmias, structural cardiac diseases, others); (2) orthostatic hypotension (due to drugs, hypovolemia, primary or secondary autonomic failure, others); (3) neurally mediated syncope (cardioinhibitory, vasodepressor, and mixed forms). Rarely neurologic disorders (such as epilepsy, transient ischemic attacks, and the subclavian steal syndrome) can lead to cerebal hypoperfusion and syncope. Nonsyncopal TLOC may be due to neurologic (epilepsy, sleep attacks, and other states with fluctuating vigilance), medical (hypoglycemia, drugs), psychiatric, or post-traumatic disorders. Basic diagnostic workup of TLOC includes a thorough history and physical examination, and a 12-lead electrocardiogram (ECG). Blood testing, electroencephalogram (EEG), magnetic resonance imaging (MRI) of the brain, echocardiography, head-up tilt test, carotid sinus massage, Holter monitoring, and loop recorders should be obtained only in specific contexts. Management strategies involve pharmacologic and nonpharmacologic interventions, and cardiac pacing.

Classic phenotype of Coffin-Lowry syndrome in a female with stimulus-induced drop episodes and a genotype with preserved N-terminal kinase domain

An adolescent female presented with intellectual disability, stimulus-induced drop episodes (SIDEs), facial characteristics that include wide set eyes, short nose with wide columella, full and everted lips with wide mouth and progressive skeletal changes: scoliosis, spondylolisthesis and pectus excavatum. These findings were suggestive of Coffin-Lowry syndrome (CLS), and this was confirmed by the identification of a novel mutation in RPS6KA3, a heterozygous one basepair duplication at nucleotide 1570 (c.1570dupA). This mutation occurs within the C-terminal kinase domain of the protein, and, therefore contradicts the previous report that SIDEs is only associated with premature truncation of the protein in the N-terminal kinase domain or upstream of this domain. As CLS is X-linked, it is unusual for a female to have such a classic phenotype.

Symptomatic narcolepsy, cataplexy and hypersomnia, and their implications in the hypothalamic hypocretin/orexin system

Human narcolepsy is a chronic sleep disorder affecting 1:2000 individuals. The disease is characterized by excessive daytime sleepiness, cataplexy and other abnormal manifestations of REM sleep, such as sleep paralysis and hypnagogic hallucinations. Recently, it was discovered that the pathophysiology of (idiopathic) narcolepsy-cataplexy is linked to hypocretin ligand deficiency in the brain and cerebrospinal fluid (CSF), as well as the positivity of the human leukocyte antigen (HLA) DR2/DQ6 (DQB1*0602). The symptoms of narcolepsy can also occur during the course of other neurological conditions (i.e. symptomatic narcolepsy). We define symptomatic narcolepsy as those cases that meet the International Sleep Disorders Narcolepsy Criteria, and which are also associated with a significant underlying neurological disorder that accounts for excessive daytime sleepiness (EDS) and temporal associations. To date, we have counted 116 symptomatic cases of narcolepsy reported in literature. As, several authors previously reported, inherited disorders (n=38), tumors (n=33), and head trauma (n=19) are the three most frequent causes for symptomatic narcolepsy. Of the 116 cases, 10 are associated with multiple sclerosis, one case of acute disseminated encephalomyelitis, and relatively rare cases were reported with vascular disorders (n=6), encephalitis (n=4) and degeneration (n=1), and hererodegenerative disorder (three cases in a family). EDS without cataplexy or any REM sleep abnormalities is also often associated with these neurological conditions, and defined as symptomatic cases of EDS. Although it is difficult to rule out the comorbidity of idiopathic narcolepsy in some cases, review of the literature reveals numerous unquestionable cases of symptomatic narcolepsy. These include cases with HLA negative and/or late onset, and cases in which the occurrences of the narcoleptic symptoms are parallel with the rise and fall of the causative disease. A review of these cases (especially those with brain tumors), illustrates a clear picture that the hypothalamus is most often involved. Several cases of symptomatic cataplexy (without EDS) were also reported and in contrast, these cases appear to be often associated with non-hypothalamic structures. CSF hypocretin-1 measurement were also carried out in a limited number of symptomatic cases of narcolepsy/EDS, including narcolepsy/EDS associated with tumors (n=5), head trauma (n=3), vascular disorders (n=5), encephalopathies (n=3), degeneration (n=30), demyelinating disorder (n=7), genetic/congenital disorders (n=11) and others (n=2). Reduced CSF hypocretin-1 levels were seen in most symptomatic narcolepsy cases of EDS with various etiologies and EDS in these cases is sometimes reversible with an improvement of the causative neurological disorder and an improvement of the hypocretin status. It is also noted that some symptomatic EDS cases (with Parkinson diseases and the thalamic infarction) appeared, but they are not linked with hypocretin ligand deficiency. In contrast to idiopathic narcolepsy cases, an occurrence of cataplexy is not tightly associated with hypocretin ligand deficiency in symptomatic cases. Since CSF hypocretin measures are still experimental, cases with sleep abnormalities/cataplexy are habitually selected for CSF hypocretin measures. Therefore, it is still not known whether all or a large majority of cases with low CSF hypocretin-1 levels with CNS interventions, exhibit EDS/cataplexy. It appears that further studies of the involvement of the hypocretin system in symptomatic narcolepsy and EDS are helpful to understand the pathophysiological mechanisms for the occurrence of EDS and cataplexy.

The movement disorders of Coffin-Lowry syndrome

Coffin-Lowry syndrome (CLS) is an X-linked semi-dominant condition with learning difficulties and dysmorphism caused by mutations in the gene RSK2. Originally, epilepsy was reported as a feature. We and others have since described predominantly sound-startle induced drop attacks that have been labelled 'cataplexy', abnormal startle response and hyperekplexia. We sought to clarify why there should be controversy over the type of paroxysmal events. Review of the literature and our patients confirmed that each centre had studied only a small numbers of individuals (mean = 2). The type of movement disorder varied both with age and between individuals. One individual might have more than one movement disorder. One of our adult patients had several types of movement disorder and epilepsy that merged seamlessly: there was true cataplexy triggered by telling a joke, something close to cataplexy ('cataplexy') triggered by sound-startle, a predominantly hypertonic reaction varying from hyperekplexia to a more prolonged tonic reaction resembling startle epilepsy, and true unprovoked epileptic seizures. In the large database of the Coffin-Lowry Syndrome Foundation family support group, 34 of 170 (20%) individuals with CLS and known age had 'drop attacks' and an additional 9 (5%) of these had additional epileptic seizures. The onset of such events was usually after age 5 years, prevalence peaking at 15-20 years (27%). Many became wheelchair bound as a result. This unique combination of more than one non-epileptic movement disorder and epilepsy deserves further semiological and genetic study both for the patients with CLS and for the wider implications.

RSK2 gene mutations in Coffin-Lowry syndrome with drop episodes

Coffin-Lowry syndrome is an X-linked mental retardation disorder with dysmorphism caused by mutation of the ribosomal S6 kinase (RSK2) gene. Coffin-Lowry syndrome patients can experience unusual drop episodes whereby an abrupt loss of muscle tone and falling down can be induced by sudden, unexpected tactile or auditory stimuli. We detected a C913T (R305X) mutation in a female Coffin-Lowry syndrome patient with drop episodes. All mutations in our patient and those previously reported in patients with drop episodes result in premature truncation of the RSK2 protein in the N-terminal kinase domain or upstream of this domain.

Postmortem findings in the Coffin-Lowry Syndrome

The Coffin-Lowry Syndrome (CLS) is a congenital disorder that can be recognized by retarded growth and development, the characteristic appearance of the face and hands, and often by the typical deformities of the back and chest; there are many other anomalies. The history of the syndrome is reviewed, noting the x-linked semidominant pattern of inheritance, and two autopsies are presented and compared with the three autopsy reports that have been published previously. The five young patients died at ages between 18 to 28 years of advancing pneumonia, aspiration of food into the trachea, or postoperative complications. There were lesions or abnormalities in the heart, brain, lungs, liver, skeleton, kidneys, intestines, and other organs. Molecular geneticists have located the CLS gene or Rsk-2 gene at Xp22.2 and demonstrated that it works by influencing the activation of other genes. The "monopolygenic" pattern may help to explain the large number of seemingly unrelated abnormalities that make up this syndrome.

Stimulus-induced drop episodes in Coffin-Lowry syndrome

OBJECTIVE

Coffin-Lowry syndrome (CLS) is a rare disorder characterized by moderate to severe mental retardation, facial dysmorphism, tapering digits, and skeletal deformity. Paroxysmal drop attacks occur in patients with CLS, characterized by sudden loss of muscle tone induced by unexpected tactile or auditory stimuli. Our objective is to characterize these attacks better using neurophysiologic studies.

METHODS

We report 2 teenage boys with CLS and stimulus-induced drop episodes (SIDEs). Simultaneous surface electromyogram (EMG) and video electroencephalogram were performed during SIDEs on our 2 patients.

RESULTS

Both patients had SIDEs stimulated by a loud noise, unexpected light touch stimulation, or visual threat that were characterized by abrupt episodes of complete or partial loss of lower extremity tone. These events were not associated with impairment of consciousness, and immediate recovery was noted. Simultaneous surface EMG and video electroencephalogram revealed no epileptiform discharges in either patient. In the first patient, after unexpected tactile or auditory stimulation, tonic EMG activity in paraspinal muscles was lost briefly, similar to that seen in cataplexy. In the second patient, at 6 years of age, sudden nonepileptic drop episodes were induced by an unexpected tactile, auditory, or visual stimulation. At 11 years of age, his episodes had changed to brief myoclonic jerk and tonic spasm that were triggered by unexpected tactile and auditory stimuli. An increase in tonic EMG activity occurred during the attacks, consistent with hyperekplexia.

CONCLUSIONS

Our data suggest that SIDEs in CLS are a heterogeneous group of nonepileptic events that may manifest features of both cataplexy and hyperekplexia, even in the same patient.

Coffin-Lowry syndrome: clinical and molecular features

The Coffin-Lowry syndrome (CLS) is a rare X linked disorder in which affected males show severe mental retardation with characteristic dysmorphism, most notably affecting the face and hands. The typical facial features consist of a prominent forehead, hypertelorism, a flat nasal bridge, downward sloping palpebral fissures, and a wide mouth with full lips. Mild progression in facial coarsening occurs during childhood and adult life. The hands are broad with soft, stubby, tapering fingers. Other clinical findings include short stature (95%), a pectus deformity (80%), a kyphosis and/or scoliosis (80%), mitral valve dysfunction, and sensorineural hearing loss. The causal gene, RSK2, was identified in 1996 and contains 22 exons which encode a protein of 740 amino acids. Over 75 distinct pathogenic mutations have been identified in 250 unrelated CLS patients.

Coffin-Lowry syndrome: a 20-year follow-up and review of long-term outcomes

The Coffin-Lowry syndrome has become well established since the first report of affected patients by Coffin et al. [1966: Am J Dis Child 112:205-213]. Since that time over a hundred cases have been reported and the responsible gene has been identified. However, there remains a paucity of long-term follow-up information on older patients with which to counsel affected families about prognosis. There is also much to be learned about genotype-phenotype correlations. In 1982 we reported 12 patients (including carrier mothers) from eight families, one of whom had died about the time the paper was written. Recently, we have been able to obtain follow-up information on six of the affected patients and one of the carrier mothers. A number of important complications have occurred, including premature death, loss of ambulation, and quadriplegia. This paper updates the medical histories of our patients and summarizes the clinically important complications that have been reported in patients with Coffin-Lowry syndrome. There are few data on patients over the age of 30, and much more longer term follow-up is required.