Abstract
Chiari malformation type I (CMI) is a structural abnormality characterized by cerebellar tonsil herniation through the foramen magnum, often leading to disrupted cerebrospinal fluid dynamics and syringomyelia. While CMI commonly presents with occipital headaches and neck pain, atypical manifestations, such as bilateral foot drops, are exceedingly rare. We describe a 37-year-old female patient presenting with bilateral foot drop, which was later established to be caused by syringomyelia secondary to CMI. Magnetic resonance imaging revealed an 8 mm tonsillar descent and a syrinx extending to the conus medullaris. The patient refused surgical intervention and opted for conservative management; partial functional recovery was subsequently observed. This report emphasizes the importance of recognizing rare neurological presentations of CMI. To our knowledge, this is the first documented case of CMI with syringomyelia presenting as a bilateral foot drop.
-
Keywords: Peroneal Neuropathies; Foot Drop; Arnold-Chiari Malformation; Syringomyelia; Case Reports
Introduction
Chiari malformation type I (CMI) is a congenital structural anomaly characterized by downward displacement of the cerebellar tonsils through the foramen magnum, leading to cerebrospinal fluid (CSF) flow disruption and the potential development of syringomyelia. A systematic review published in 2017 on the natural history of CMI revealed that common presenting symptoms include headaches (both cough and migraine types), paresthesia, cerebellar symptoms, dysphagia, cranial nerve dysfunction, occipital headaches, neck pain, and balance disturbances [
1]. Rarely, atypical neurological presentations, such as isolated lower limb weakness or foot drop, may rarely occur, complicating the diagnostic process.
Although rare, bilateral foot drop is a significant clinical finding indicative of central nervous system involvement. This condition results from motor pathway dysfunction and is often linked to spinal cord lesions or corticospinal tract damage. Syringomyelia, a frequent complication of CMI, involves the formation of a fluid-filled cavity within the spinal cord that can compress neural structures and cause motor and sensory deficits. Recognizing these atypical presentations is essential for a timely diagnosis and appropriate management. This report presents a rare case of CMI with extensive syringomyelia manifesting as bilateral foot drop, a clinical scenario that remains under-reported in the literature.
Case Report
A 37-year-old female patient presented to a primary care clinic in July 2022 with a 3-week history of progressive difficulty in ambulation, characterized by bilateral lower extremity weakness. She reported prior episodes of non-specific headaches triggered by coughing, but denied any history of trauma, chronic headache, back pain, or other neurological symptoms. The patient had a history of smear-positive pulmonary tuberculosis for which she completed a 9-month course of anti-tuberculosis treatment in 2021. Her childhood and developmental histories were unremarkable.
Neurological examination revealed marked bilateral foot drop with a muscle strength of 0/5 in dorsiflexion and 3/5 in plantar flexion, along with mild weakness in bilateral knee and hip extension and flexion with 4/5 muscle strength. Reflex testing demonstrated hyperreflexia in both knees, with normal plantar reflexes. Sensory examination revealed a diminished pinprick sensation over the left distal leg, predominantly in the L5 dermatome, whereas other dermatomes, including those of the right leg, were intact. She exhibited a high-stepping, broad-based gait with subtle truncal intubation while sitting. Other neurological findings were unremarkable, and there were no disturbances in the bladder or bowel function. The patient was initially referred to a tertiary center with a provisional diagnosis of Guillain-Barre syndrome.
Upon further evaluation at the tertiary center, laboratory investigations including complete blood count, erythrocyte sedimentation rate, and C-reactive protein level were unremarkable. CSF analysis and tuberculosis workup results were negative, ruling out central nervous system infections and inflammatory conditions. Radiographs of the lumbosacral spine revealed no abnormalities. The nerve conduction studies (NCS) were normal, suggesting intact function of the bilateral common fibular and tibial nerves, with no evidence of peripheral neuropathy. Magnetic resonance imaging (MRI) of the brain and spine revealed an 8 mm herniation of the cerebellar tonsils through the foramen magnum (
Figure 1) accompanied by extensive syringohydromyelia extending from the cervicomedullary junction to the conus medullaris (
Figures 2,
3). These findings confirmed the diagnosis of CMI.
The patient was referred to the neurosurgical team for decompression of the posterior fossa. However, the patient declined surgical intervention owing to personal preferences and opted for conservative management. Treatment included a neurorehabilitation program that focused on muscle strengthening, balance enhancement, and gait retraining. An ankle-foot orthosis was prescribed to improve mobility and support foot positioning. Initially requiring a quadripod for ambulation, the patient began to use a walking stick as her condition improved. Over 2 months, she demonstrated significant recovery, including improved dorsiflexion strength with a power of 3/5, reduced high-stepping gait, and normalization of sensory function. Given her symptomatic improvement with conservative management and the absence of new or worsening neurological symptoms, a repeat brain MRI was not performed. Follow-up imaging was planned only if new symptoms developed, current symptoms worsened, or the patient opted for surgical intervention. The patient provided written informed consent for the publication of research details and clinical images.
Discussion
CMI is defined by a cerebellar tonsillar descent of 5 mm or more below the foramen magnum. It has a bimodal age distribution, with peaks in children aged 8–9 years and adults aged 41–46 years, and a marked female predominance, particularly in adults, where female patients account for 85.9% of cases [
1]. CMI commonly presents with a spectrum of symptoms, the most frequent being headaches, reported in up to 93.5%, neck pain at 29.4%, bulbar symptoms at 16.5%, and ocular disturbances at 14.1% [
1]. Syringomyelia, a common complication of CM1, is seen more frequently in pediatric patients (65.4%) compared to adults (36.5%) [
1]. Syringomyelia often presents with symptoms like sensory dissociation, characterized by a “cape-like” distribution of sensory loss, motor weakness, and spasticity [
2].
CMI occurs because of structural abnormalities in the posterior fossa, causing the cerebellar tonsils to herniate through the foramen magnum. This disrupts CSF flow, causing pressure changes that push fluid into the spinal cord and form a syrinx. The resulting syringomyelia compresses the adjacent neural structures, particularly the corticospinal tract, and causes motor and sensory deficits. In the present case, extensive syrinx accounted for the patient’s bilateral foot drops and spasticity. This case aligns with the existing literature on CMI and syringomyelia but also highlights a rare manifestation of bilateral foot drop. Previous studies have documented syringomyelia-related motor deficits, especially unilateral foot drop [
3-
5] but bilateral lower limb involvement remains uncommon [
6].
Neuroimaging plays a pivotal role in the diagnosis of CMI and its associated complications. MRI is the gold standard for high-resolution visualization of cerebellar tonsillar descent and syrinx formation [
7]. In this case, the patient presented with progressive bilateral foot drop in the absence of trauma, chronic headache, or systemic symptoms. Normal lumbar puncture and NCS findings excluded the possibility of peripheral neuropathy. CSF analysis was negative for
Mycobacterium tuberculosis and other infectious or inflammatory markers, effectively ruling out central nervous system infections, such as tuberculous meningitis. MRI of the brain and whole spine revealed hallmark features of CMI—an 8 mm cerebellar tonsillar descent through the foramen magnumand associated extensive syringomyelia extending from the cervicomedullary junction to the conus medullaris.
The management of CMI depends on symptom severity. While asymptomatic or minimally symptomatic patients may be managed conservatively with regular monitoring, surgical decompression is the preferred intervention for progressive or disabling symptoms [
7]. Posterior fossa decompression is the most common surgical approach, with studies showing symptom improvement in 75% of adults and 94.4% of pediatric patients [
1]. However, surgical outcomes vary and persistent syrinx formation or residual neurological deficits may occur in long-standing cases [
7]. In this case, the patient opted for conservative management, including physiotherapy and mobility aids, which led to functional improvement.
This case emphasizes the importance of considering CMI in patients presenting with unexplained motor deficits and highlights the role of neuroimaging in early diagnosis. Although surgical decompression remains the standard treatment for progressive disease, carefully selected patients may benefit from conservative management.
Notes
Figure. 1.Sagittal T2-weighted magnetic resonance imaging of the cranio-vertebral junction and cervical spine demonstrates descent of the cerebellar tonsils below the foramen magnum (red arrow) and syringomyelia (green arrow). This is associated with Chiari malformation type I. The image also shows dilatation of the lateral, third and fourth ventricles (yellow arrows).
Figure. 2.Sagittal T2-weighted magnetic resonance imaging of the cervico-thoracic spine demonstrating syringomyelia extending from the cervico-medullary junction and extending down to the thoracic vertebra, with numerous septations seen within the syringomyelia (red arrows).
Figure. 3.Sagittal T2-weighted magnetic resonance imaging of the lumbo-sacral spine demonstrates extensive syringomyelia extending down to the conus medullaris (red arrow).
References
- 1. Langridge B, Phillips E, Choi D. Chiari malformation type 1: a systematic review of natural history and conservative management. World Neurosurg 2017;104:213-9.
- 2. Mortazavi A, Almeida ND, Hofmann K, Davidson L, Rotter J, Phan TN, et al. Multicenter comparison of Chiari malformation type I presentation in children versus adults. J Neurosurg Pediatr 2024;34:49-56.
- 3. Ciaramitaro P, Garbossa D, Peretta P, Piatelli G, Massimi L, Valentini L, et al. Syringomyelia and Chiari Syndrome Registry: advances in epidemiology, clinical phenotypes and natural history based on a North Western Italy cohort. Ann Ist Super Sanita 2020;56:48-58.
- 4. Panda AK, Kaur M. Rapidly progressive foot drop: an uncommon and underappreciated cause of Chiari I malformation and holocord syrinx. BMJ Case Rep 2013;2013:bcr2013009644.
- 5. Higuchi N, Nakamura T, Yoshioka F, Sanefuji M, Matsuo M. Two differential cavities in syringomyelia of pediatric Chiari I malformation presenting with unilateral foot drop. Brain Dev 2023;45:191-5.
- 6. Jayamanne C, Fernando L, Mettananda S. Chiari malformation type 1 presenting as unilateral progressive foot drop: a case report and review of literature. BMC Pediatr 2018;18:34.
- 7. Saifudheen K, Jose J, Gafoor VA. Holocord syringomyelia presenting as rapidly progressive foot drop. J Neurosci Rural Pract 2011;2:195-6.
Figure & Data
Citations
Citations to this article as recorded by
, Suraya Abdul-Razak1,2*
