Pediatric Arnold-Chiari I Malformation With Syrinx Presenting With Unilateral Hand Weakness: A Case Report

Introduction

Arnold-Chiari I malformations (CM-I) are characterized by the caudal displacement of the cerebellar tonsils into the foramen magnum, defined as a herniation greater than 5 mm.^1,2 This displacement can lead to impairments from compression of the brainstem and cervical spinal cord, as well as cerebrospinal fluid irregularities from cerebral aqueduct blockage, contributing most commonly to syringomyelia found on imaging. ² The incidence of CM-I is estimated to be between 0.24% and 3.6%, and the onset of symptoms is typically around the second or third decade of life with an average age at presentation for syringomyelia-related symptoms of 35.^3,4 Presentations for CM-I are quite variable, especially so for the pediatric population, ranging from posterior occipital headaches to neck pain and upper extremity numbness, all of which are often worsened with the Valsalva maneuver. Few differences in clinical symptoms exist between the adult and pediatric populations, with the exception of sleep apnea and feeding difficulty in young children. Pain is by far the most common presenting symptom in 60% to 70% of pediatric cases, and headache is the most common complaint throughout the disease course. ² Within the pediatric population, syrinx formation is found in 30% to 85% of CM-I with older children more likely to be symptomatic, likely as a thorough history and physical findings are more difficult in this population.^1,2,4 Pediatric patients with CM-I are also more likely to initially present to their pediatrician or an orthopedist, so early detection is crucial to limit delays in diagnosis.

Although there are more pediatric patients being diagnosed with CM-I earlier, due to increased understanding of the disease process and common presentations, patients in this population are less likely to present with sensory disturbances and motor weakness compared with headaches and neck pain. ⁵ Thorough neurologic examination may be more challenging in the pediatric population, and clinicians may be less inclined to expect cervical and/or central causes that are more common in the adult population, including cervical degeneration, stroke, or more rarely CM-I. ⁶ Thus, pediatric patients with primarily neurological complaints may not be adequately evaluated. Therefore, we report a case of an adolescent male with chronic unilateral hand numbness and weakness presenting to an outpatient orthopedic hand clinic who was ultimately found to have CM-I with cervical spine syrinx formation.

Case Description

History and Presentation

The patient was a 14-year-old left-hand-dominant adolescent boy who presented to the orthopedics outpatient clinic. His medical history was notable for mild scoliosis and acute lymphoblastic leukemia treated with chemotherapy at age 3. At the time of presentation, the patient reported 6 months of right-hand weakness, as well as numbness, pain, and tingling in the right wrist and hand. This progressed to impaired dexterity and grasping strength on the right side. During a transient viral illness, the patient also noticed his numbness and upper extremity discomfort worsened when he coughed. His hand paresthesia was predominantly in the median nerve distribution and was partially relieved by his mother’s carpal tunnel splint. He had initially presented to his pediatrician with these upper extremity symptoms, but no further diagnostic steps were taken. He then presented to orthopedic hand clinic, joining his mother for her appointment.

Physical examination at that time was notable for mild, mixed ulnar and radial nerve dysfunction with 4/5 strength of the right interossei and 4+/5 strength with wrist and finger extension. He exhibited a dynamic clawing posture to his right hand. Radial side wrist extensors were stronger than those of the ulnar side. The patient had full active and passive range of motion of the wrist and fingers at all distal joints, as well as intact and symmetric sensation throughout all fingertips. Given his viral illness and associated symptoms, differential diagnosis included a chronic brachial neuritis (Parsonage Turner syndrome) or a neuralgic amyotrophy. Neurodiagnostic testing, including electromyography (EMG) and nerve conduction velocity, was obtained on the same day he presented to hand clinic.

His EMG results demonstrated mildly reduced recruitment of the C7 and C8 myotomes consistent with mild right C7 and C8 radiculopathies without evidence of peripheral nerve dysfunction or right brachial plexopathy. Within 1 week of initial presentation, magnetic resonance imaging (MRI) without contrast of the cervical spine was performed and demonstrated a Chiari I malformation with cerebellar tonsillar descent of 2.2 cm with associated caudal descent of the medulla oblongata (Figure 1a). In addition, there was an expansile central intramedullary syrinx beginning at the level of C2, measuring at least 0.9 × 1.4 cm with a predominant T1 hypointense signal (Figure 1b). He was subsequently seen by pediatric neurosurgery who confirmed the diagnosis, with an additional finding of impaired range of motion in dorsiflexion of the right ankle. Magnetic resonance imaging of the brain and entire spine without contrast further characterized the hydrosyringomyelia as extending from the craniocervical junction to the level of T9 to T10, with internal septations at C2 and crowding at the craniocervical junction (Figure 2).

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Figure 1.

Preoperative magnetic resonance imaging of the cervical spine.

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Figure 2.

Preoperative magnetic resonance imaging of the brain and entire spine.

Operative Intervention and Postoperative Course

Operative options included a classic Chiari decompression with or without a craniocervical junction fusion given the basilar invagination and posterior angled dens found on imaging. The family decided to proceed with a classic Chiari decompression without a craniocervical fusion. The surgery and postoperative course were uncomplicated. The patient was discharged home on postoperative day 3 with a plan for outpatient physical therapy (PT).

The patient was seen in follow-up 1 month after surgery with subjective and objective improvement in hand strength, dexterity, and function. He showed less right-hand clawing and a normal gait. He continued to show impairments in right ankle dorsiflexion impairment, specifically in range of motion and strength. A postoperative MRI was performed 3 months after surgery, which demonstrated an appropriate posterior fossa decompression (Figure 3). There was improvement in craniocervical junction crowding and morphology of the cerebellar tonsils. The expansive syrinx was reduced to 0.65 cm in diameter from 1 cm, and the C2 loculations were reduced to a residual cystic component. The patient met most of his outpatient PT goals 6 months after surgery, with markedly improved right upper extremity strength and absence of pain during exercise. His balance returned to his baseline. He had residual impairments in grip strength and fine motor tasks, which are being further managed with occupational therapy.

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Figure 3.

Postoperative magnetic resonance imaging of the brain and entire spine.

Discussion

Many clinical features in this case were atypical for CM-I presentations in the pediatric population. It has been shown that primary symptoms of sensory disturbance and motor weakness, as well as syringomyelia, found on imaging are significantly less common at initial presentation in pediatric patients compared with adults. ⁵ Although these kinds of signs are more difficult to elicit in children, examination findings for CM-I can often be missed given the potentially complex sensory disturbances combined with immature communication skills. ⁵ In addition, as most symptomatic cases of CM-I are found in adult patients, pediatric cases are typically found incidentally during workup of another condition like new-onset seizures, making diagnostic evaluation challenging.^7,8 For symptomatic cases of pediatric patients with CM-I, it has been shown in the literature that headache is the most common symptom, particularly in the occipital region. These headaches often worsen while coughing or sneezing due to an increase in intracranial pressure. ² Other more common presentations include scoliosis, nystagmus, and sleep apnea due to brain stem compression and even social developmental delay as the cerebellum is proposed to play a role in social cognition.^{3,5,8 -10} In patients with associated syringomyelia, the most common symptom includes dissociated sensory disturbance, particularly an isolated loss of pain and temperature sensation. ¹⁰ Other symptoms include muscle atrophy and upper motor neuron loss manifesting as spasticity and urinary and bowel incontinence.^5,10

In this case, the initial presentation was isolated unilateral hand symptoms. He did not express the classic headache or neck pain described in most of the pediatric cases, and there were no upper motor neuron findings often found in patients with cervical syrinx formation. A retrospective study of 84 patients with CM-I who underwent surgical treatment found that 18.9% of the patients had sensory disturbance at presentation, and likely this prevalence is much lower without other commonly associated symptoms. ⁵ Certainly, this case represents an atypical presentation of symptomatic CM-I in the pediatric population. In addition, given his presentation initially to his pediatrician, CM-I did not appear to be at first in the differential diagnosis. Although headache is the most common presenting symptom, it is possible that especially in the pediatric population, numbness, tingling, and patchy neurologic symptoms without pain may be present more often but not alarming enough to seek medical attention. We urge for further studies of diagnosed CM-I pediatric patients, particularly retrospectively inquiring about other symptoms before the diagnosis that did not alert the patient or caregiver to seek medical attention. This points to the importance of early investigatory tools such as neurodiagnostic testing and advanced imaging when neurologic symptoms are present, even if they are vague in nature. The threshold to order a neurodiagnostic examination may be higher in the pediatric population because the test can be uncomfortable. The threshold may be higher for MRI in the younger patient because sedation may be required. However, this diagnostic information could help to prevent extended time to diagnosis and potentially permanent neurologic symptoms.

With a careful history, symptoms that can seem vague, insignificant, or inconsistent with peripheral pathology when considered in isolation may make sense in retrospect when a central nervous system cause is included in the differential. For example, the symptoms in this case started with a sensory disturbance with subsequent motor dysfunction and impaired dexterity, which indicated a neurologic dysfunction outside of a specific dermatome or myotome. This was corroborated by the mixed upper extremity nerve impairment found on neurological examination. ¹¹ Further history revealed a transient headache and ipsilateral neck pain during a viral illness could have represented worsened brainstem compression triggered by acute inflammation in the area; similar hypotheses for CM-I have been described in the literature. ¹² The high suspicion of a central neurological process combined with the concerning neurological examination ultimately led to further diagnostic testing and eventual surgical treatment. However, the initial treatment approach was observation. Ideally, further evaluation at initial presentation may help limit permanent residual deficits.

Other reports in the literature have described CM-I with syringomyelia leading to isolated symptoms, including vocal cord paralysis, orofacial pain, median nerve dysfunction presenting as carpal tunnel syndrome, snoring, and social impairment.^{8,12 -14} Thus, especially in the pediatric population, presentations are quite variable, making clinical suspicion and a thorough neurological examination crucial. The patient’s symptoms also were on his non-dominant side, which can make symptom identification and impairment more difficult to detect. Within medicine, it is common to dismiss symptoms when the clinical findings cannot be reconciled with the expected neurologic anatomic distribution. In addition, neurodiagnostic testing is not a common test ordered in the pediatric population. Clinicians should not be deterred from neurologic symptoms that do not align with a particular diagnosis or symptom syndrome but rather consider early neurologic referral or neurodiagnostic testing. It is crucial to bear in mind the time to diagnosis to avoid permanent neurologic dysfunction.

Complications associated with a later CM-I diagnosis can include worsening debilitating headaches, further brainstem compression leading to central sleep apnea, visual disturbances, breathing challenges, and even life-threatening paralysis. ¹⁵ A prolonged diagnostic evaluation can potentially lead to an incompletely operable status or symptoms that may not resolve postoperatively, indicating an overall worse prognosis. Neurodiagnostic testing through an EMG, for example, is also less commonly used in the pediatric population; however, it allowed for further clarification of CM-I in this case. It may also be beneficial in improving diagnostic clarity, especially for atypical presentations.

Of course, each pediatric CM-I presentation is unique, and diagnostic evaluation remains challenging. However, actionable improvements in assessment of unexplained neurological symptoms including a thorough neurologic examination and obtaining a meticulous history can lead to earlier detection of CM-I and prompt treatment while preventing long-term complications. Although this case resulted in successful decompression and treatment, it is possible that earlier initiation of evaluation and treatment may have resulted in less residual neurologic impairment. We seek to highlight the value of a low threshold for early neurodiagnostic testing or neurology referral even for minimally bothersome neurologic symptoms, even when those symptoms are not fitting into an expected neuroanatomic distribution. A “wait and see” approach may ultimately lead to a less optimal outcome with permanent neurologic deficits. Chiari I malformation presents in all realms of clinical medicine and may not always present with predictable symptoms, so we urge consideration of causes like CM-I especially in pediatric cases with an indeterminate neurological picture.

Conclusions

This case highlights the importance of identifying atypical presentations of CM-I—weakness in a pediatric patient. History and physical findings are challenging to elicit in this patient population, especially when symptoms are not overwhelmingly associated with pain. Their symptoms are more likely to be dismissed when they do not fit certain diagnostic criteria or fall into a natural anatomical distribution, especially when initially presenting outside of a neurology clinic. We urge the importance of a thorough neurological examination and considering CM-I in pediatric patients presenting with central and/or peripheral nervous system dysfunction, as delays in treatment could carry a poorer prognosis.