|Year : 2016 | Volume
| Issue : 1 | Page : 51-53
Joubert syndrome misdiagnosed as hypotonic cerebral palsy: Confirmation by magnetic resonance imaging
Ghanshyam Dev, Mohd Ilyas, Sonali Sharma
Department of Radiodiagnosis and Imaging, Government Medical College, Jammu and Kashmir, India
|Date of Web Publication||10-Aug-2016|
Lane 22, House No. 38, Tawi Vihar, Sidhra,Jammu 180 019, Jammu and Kashmir
Source of Support: None, Conflict of Interest: None
Joubert syndrome is a rare autosomal recessive condition characterized by hypotonia, ataxia, psychomotor delay, and variable occurrence of oculomotor apraxia and neonatal breathing abnormalities. We report a 7-year-old female child who was referred to our department as a case developmental delay and hypotonia due to hypotonic cerebral palsy for magnetic resonance imaging (MRI) of the brain. MRI of the brain revealed typical molar tooth sign, bat wing appearance of the fourth ventricle, and dysgenesis of the superior cerebellar vermis. Determination of the symptoms, early diagnosis, and genetic consultation are the goals for decision-making to begin treatment and rehabilitation programs.
Keywords: Bat wing sign, cerebral palsy, developmental delay, Joubert syndrome, molar tooth sign, superior cerebellar vermis dysgenesis
|How to cite this article:|
Dev G, Ilyas M, Sharma S. Joubert syndrome misdiagnosed as hypotonic cerebral palsy: Confirmation by magnetic resonance imaging. Indian J Cereb Palsy 2016;2:51-3
|How to cite this URL:|
Dev G, Ilyas M, Sharma S. Joubert syndrome misdiagnosed as hypotonic cerebral palsy: Confirmation by magnetic resonance imaging. Indian J Cereb Palsy [serial online] 2016 [cited 2017 Apr 23];2:51-3. Available from: http://www.ijcpjournal.org/text.asp?2016/2/1/51/188165
| Introduction|| |
Joubert syndrome is characterized by congenital cerebellar ataxia, hypotonia, oculomotor apraxia, intellectual disability, and specific mid-hindbrain malformation ("molar tooth sign"). Clinically, it is difficult to differentiate between hypotonic cerebral palsy (CP) and Joubert syndrome. Magnetic resonance imaging (MRI) forms the cornerstone to prevent this mistake. Joubert syndrome is associated with the molar tooth sign, a radiologic finding that includes cerebellar vermis hypoplasia or dysplasia, thick and horizontally oriented superior cerebellar peduncles, and an abnormally deep interpeduncular fossa, and bat wing appearance of the fourth ventricle. 
| Case report|| |
A 7-year-old female child presented to the pediatric outpatient clinic with developmental delay. Parents noticed that the child was not able to keep up with developmental milestones up to 5 years of age and consulted at district hospital where she was labeled as hypotonic CP by attending physician there (who was not a pediatrician). Now, they reported to our medical college. She had social smile at 3 months and head control at 5 months of age and was able to sit with support only at 12 months. She was able to walk with difficulty at 3½ years.
There was no history of perinatal insult, seizure, abnormal breathing pattern, feeding, or swallowing difficulty. She was born at term to nonconsanguineous parents and suffered no significant perinatal asphyxia. She was the second child of her parents. The first child was a normal male child.
On examination, she was awake, alert. Ocular examination was normal. She showed mild facial dysmorphism in the form of forehead prominence. There was no organomegaly. Heart and lungs were normal on auscultation. Neurological examination revealed normal cranial nerves and fundus. Motor examination revealed hypotonia. She was referred to our department for MR scanning of the brain which was performed using 1.5 Tesla Siemens Magnetom machine (Siemens Healthcare, Germany).
The axial T1- and T2-weighted MRIs showed abnormally oriented and thickened superior cerebellar peduncles that appeared as a molar tooth configuration [Figure 1]. The more caudal T2- and T1-weighted axial MRIs showed the fourth ventricle shaped like a bat wing [Figure 2]. Furthermore, T2-weighted axial and sagittal MRIs showed hypoplasia of the vermis which resulted in median approach of the two cerebellar hemispheres but without evidence of a posterior fossa cyst [Figure 3] and [Figure 4]. Based on clinical and MRI findings, diagnosis of Joubert syndrome was made, and parents were counseled. Her ultrasonography (USG) of the abdomen was normal.
|Figure 2: Magnetic resonance images showed the fourth ventricle shaped like a bat wing|
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|Figure 3: T2-weighted axial and sagittal magnetic resonance images showed hypoplasia of the vermis|
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|Figure 4: T1-weighted sagittal magnetic resonance images showed hypoplasia of the vermis|
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| Discussion|| |
Joubert syndrome was originally described in 1968 in four siblings with agenesis of the cerebellar vermis presenting with hyperpnea, abnormal eye movements, ataxia, and intellectual disability.  The incidence of Joubert syndrome has been estimated as between 1/80,000 and 1/100,000 live births. 
The clinical features frequently mentioned as essential for the diagnosis of classic Joubert syndrome comprise. 
- Hypotonia in infancy
- Developmental delay/mental retardation
- One or both of the following (not absolutely required but helpful for the diagnosis):
- Irregular breathing pattern in infancy (intermittent tachypnea and/or apnea)
- Abnormal eye movements.
These features can be easily confused with the symptoms of hypotonic CP.
This syndrome is classified into two groups on the basis of presence or absence of retinal dystrophy. Patients with retinal dystrophy have a higher prevalence of multicystic renal disease and these patients also appear to have decreased survival rates compared with those patients without retinal dystrophy.  There was no evidence of retinal disease on ophthalmological examination in our patient. USG examination of the abdomen of our patient revealed normal kidneys.
The main clinical signs of Joubert syndrome are hypotonia, ataxia, intellectual disability, abnormal eye movements, and a respiratory pattern of alternating tachypnea-apnea during the 1 st few months of life. Hypotonia and intellectual disability are the constant features of Joubert syndrome. Infants have moderate to severe hypotonia. Most studies list hypotonia as one of the major findings of the disease.
The hallmark imaging features of Joubert syndrome are as follows:
- Dysgenesis of the isthmus (part of the brainstem between the pons and inferior colliculus), which is seen as elongation and thinning of the pontomesencephalic junction, and deep interpeduncular fossa
- Thickening of the superior cerebellar peduncles
- Hypoplasia of the vermis characterized by incomplete lobulation and enlarged fourth ventricles
- Incomplete fusion of the halves of the vermis, creating a sagittal vermis cleft seen on axial or coronal MRI planes.
Combination of the first three features produces the characteristic molar tooth sign on axial MRI. Hypogenesis of the vermis results in a triangular-shaped mid-fourth ventricle and a bat wing-shaped superior fourth ventricle. 
Developmental impairment and intellectual disability are usually severe and present across a variety of domains, including behavior, motor, language, and general development. It is difficult to state the mental deficit in patients with Joubert syndrome as the cerebrum seems to be spared; mainly, the cerebellar vermis and the pontomesencephalic junction are affected by the malformation. 
Unfortunately, there are currently no curative therapies for these genetic ciliopathic syndromes. Early diagnosis of Joubert syndrome-related disorders is important for prognostic outcome and genetic consultation. Close follow-up is also necessary to identify potential complications of the disease.
| Conclusion|| |
Joubert syndrome is an important clinical condition to be considered in differential diagnosis of patients having developmental delay, ataxia, or hypotonia and it is to be differentiated from CP if no evidence of perinatal insult is found, by early MRI. The hallmark MR findings include molar tooth sign, deep interpeduncular fossa, superior cerebellar vermis agenesis/dysgenesis, and bat wing sign of the fourth ventricle.
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Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]