Head Thrusts in Two Children With Unusual Neuroimaging Findings

Clinical Correspondence Section Editors: Robert Avery, DO Karl C. Golnik, MD Caroline Froment, MD, PhD An-Guor Wang, MD Head Thrusts in Two Children With Unusual Neuroimaging Findings Michael S. Salman, MBBS, PhD, Martin Bunge, MD CASE 1 A 4.5-month-old girl was referred with right gaze preference since 6 weeks of age. She tended to look to the right with her head also deviated to the right. She could look only briefly to the left in response to visual stimuli or noise. Otherwise, she was well. She could fix and follow. She achieved head control slightly late, at the age of 3.5 months. Parents did not notice head nods and thrusts or abnormal ocular oscillations. Pregnancy was remarkable for excessive vomiting treated with Diclectin. Mom had no illnesses or toxic exposures. Delivery was unremarkable at term. Parents are second cousins of Hutterite ethnicity. On examination, she had no dysmorphic features or neurocutaneous stigmata. She fixed and followed and displayed right gaze preference with a right head turn. She was spontaneously able to bring her eyes and/or head intermittently to midline and to the left on prompting with noise or visual stimuli. The right gaze preference was overcome with the oculocephalic maneuver. When held at arm’s length and spun toward the examiner’s right side, her optokinetic response was normal. When she was spun toward the examiner’s left side, there were no saccades toward her left side. The rest of the neurological examination was normal. Brain MRI at the age of 6 months was suspicious for hypoplasia/absence of the right superior colliculus (Fig. 1). The remainder of the MRI was normal. At 10 months of age, the right gaze preference resolved. At 2 years of age, her development was normal. On examination, she could make saccades to the right but needed to either use head thrusts or blinks when she shifted her gaze rapidly to the left. Visual field testing on confrontation was normal. She did not have hypotonia or ataxia. CASE 2 A 10-month-old boy was referred with head thrusts. At 1 month of age, he appeared almost blind. Rapid head thrusts developed later on right or left gaze. Slow tracking movements were preserved. Pregnancy was remarkable for a fall at 4 months of gestation from a height of 1.5 m, resulting in a right-sided abdominal bruise. The fetus was checked, and no abnormality was found. Birth was unremarkable at term. Developmental assessment revealed mild gross motor delay. Mom had a learning disability. Family history was otherwise unremarkable. On examination, he was not dysmorphic and had no neurocutaneous stigmata. He was able to generate very small amplitude saccades in all directions but had difficulty making bidirectional, horizontal, large-amplitude saccades. Horizontal head thrusts were seen when he shifted his gaze. Horizontal and vertical smooth pursuit was jerky—an Section of Pediatric Neurology (MSS), Department of Pediatrics and Child Health, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada; and Section of Pediatric Radiology (MB), Department of Radiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada. The authors report no conflicts of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www. jneuro-ophthalmology.com). M. S. Salman conceived writing the case report. He was involved in the organization and execution of the project. He did the literature search, produced the first draft, and edited the manuscript several times. M. Bunge contributed the MRI figure and its legend, and edited (review and critique) the manuscript. Consent and ethics approval: parents gave verbal and written consent for the cases to be published. Ethical approval for reporting the cases was given by the Research Ethics Board of the University of Manitoba. Address correspondence to Michael S. Salman, MBBS, PhD, Section of Pediatric Neurology, Children’s Hospital, AE 308, 820 Sherbrook Street, Winnipeg, MB R3A 1R9, Canada; E-mail: [e-mail] Salman and Bunge: J Neuro-Ophthalmol 2022; 42: e427-e429 FIG. 1. Brain MRI of the first case performed at 6 months of age. A. T2-weighted axial image (TR: 4,560, TE: 82, slice thickness: 4 mm) showing right-sided flattening of the dorsal aspect of the brainstem in the region of the superior colliculus (arrow). B. T2-weighted coronal image (TR: 3,000, TE: 103, slice thickness: 2 mm) showing absence of the right superior colliculus (arrow). e427 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Correspondence expected finding at his age. His horizontal but not vertical optokinetic response was impaired. When he was spun to the right or left, his eyes deviated tonically toward the direction of spin as anticipated; however, no fast eye movements were observed toward the opposite direction of the spin. He had normal oculocephalic response. Pupils were equal and reactive to light, and his fundi were normal. The remainder of his cranial nerves was normal. He had central and peripheral hypotonia. Strength, coordination, and reflexes were unremarkable. At 16 months of age, head thrusts were still present. When his head was immobilized, he blinked to initiate horizontal saccades. He had normal vertical smooth pursuit and saccades; however, he had jerky smooth pursuit horizontally beyond what is anticipated for age. At 32 months of age, his language and speech were several months behind. At 53 months of age, his development was at an age-appropriate level following a formal developmental assessment apart from clumsiness. At 7 years of age, his ocular findings were unchanged. He mostly used blinks to rapidly shift his horizontal direction of gaze. His uncorrected near visual acuity was 20/20 in each eye. Visual fields and fundus examination were normal. He did not have strabismus, nystagmus, alternating skew deviation, wheelrolling torsional movements, or retinal dystrophy. Brain MRI at 15 months of age showed dysplasia/ hypoplasia involving parts of the superior cerebellar vermis. No other abnormalities were found. A repeat brain MRI at 5 years was unchanged (Fig. 2). Head thrust is a clinical sign seen in several disorders with impaired saccades, for example, Joubert syndrome and related disorders (JSRD) and ataxia telangiectasia (1). It is probably an adaptive mechanism that enables rapid ocular shift toward the direction of gaze. Head thrust is also a FIG. 2. A. Brain MRI of the second case performed at 5 years. The T1-weighted midsagittal image (TR: 2000, TE: 8, slice thickness: 5 mm) shows abnormalities in parts of the superior cerebellar vermis lobules. There are dysplastic changes (i.e., abnormal shape and “texture”) caused by abnormal folia pattern in lobule III (centralis lobule) and the anterior-most part of lobule IV (culmen lobule) (vertical arrows). In addition, there is hypoplasia of lobule III (arrowhead) causing ex vacuo enlargement of the adjacent extra axial space (oblique arrow). B. T1-weighted midsagittal brain MRI of a normal child of a similar age for comparison. e428 feature of infantile-onset saccade initiation delay (ISID), previously and erroneously named ‟congenital ocular motor apraxia” (the disorder is not manifest at birth, and there is no apraxia since reflexive saccades are typically also impaired) (1–3). In ISID, affected infants appear blind initially. Head thrusts appear after infants develop head control (3). As the child gets older, blinks are seen, when a rapid shift in gaze is required. Saccades in ISID typically have increased latency and/or are hypometric (3). The pathogenesis of ISID remains unknown (1). Unidirectional head thrusts, as seen in our first case, are uncommon in ISID and suggest a focal abnormality (2). In our second case, the clinical features described are more typical of ISID with horizontal saccade being affected bilaterally (2). The most common cause of conjugate gaze deviation with ipsiversive head turn is cortical visual impairment (4). In our first case, there was no clinical or neuroimaging evidence of injury to the posterior visual pathways. Being Hutterite, JSRD was suspected because there are specific disease-causing mutations in that population (5). However, the dysfunction in saccade initiation in JSRD is bilateral and involves horizontal and vertical saccades (1,3). None of the neuroradiological findings associated with JSRD, including the molar tooth sign, were present on MRI in our 2 cases (6). Neuroimaging in ISID may be normal or may show a variety of cerebellar or cerebral abnormalities (2). Structural and signal abnormalities on neuroimaging of the brainstem and cerebellum have been reported in ISID (See Supplemental Digital Content, Table E1, http:// links.lww.com/WNO/A462) (2,7). The published cases reporting cerebellar abnormalities refer to ‟vermis hypoplasia or dysplasia” with no further specific details (3). The brain MRIs in our 2 cases with ISID revealed novel findings. We found no similar reports of such specific and highly localized findings. The small right superior colliculus in the first case is consistent with the diagnosis of ISID in association with unilateral head thrusts because the superior colliculus is part of the neural network that processes saccades generation and head movements. Electrical stimulation of the caudal parts of the superior colliculus causes contralateral eyes and head movements (3). Her initial right conjugate gaze deviation and head turn likely correspond to the unopposed function of her intact left superior colliculus. We speculate that the MRI abnormality is not genetic because it is unilateral and may have been due to vascular insufficiency in utero. In the second case, we speculate that the MRI findings may have been caused by an intrauterine bleed in the region of the superior cerebellar vermis, possibly related to the maternal fall that occurred during pregnancy. In conclusion, infants with suspected blindness or gaze preference should have their saccades examined before labelling them as being visually impaired. A brain MRI is recommended in such infants. Salman and Bunge: J Neuro-Ophthalmol 2022; 42: e427-e429 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. 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