Chiari 1 malformation presenting with progressive, unilateral upper limb neuropathic oligoarthropathy – Connecting the dots

A 56-year-old female presented to the Orthopaedic outpatient department with complaints of recent onset left shoulder pain, swelling and restricted movements with a backdrop of long-standing left elbow painless swelling and left arm weakness (about 10 years). There was no history of fever, significant trauma, prolonged hospital admission, diabetes or any other comorbidity.

Radiograph left shoulder (Figure 1a) showed destruction of left humeral head with blunted, amputated appearance associated with sclerosis and marginal irregularity. There was associated glenoid destruction, widening of glenohumeral joint space and few peri-articular bony fragments along lateral humeral shaft.

Radiograph left elbow (Figure 1b) demonstrated destruction of left proximal radius and humeral condyles with widening of humero-ulnar joint space and sclerosis of ulnar olecranon process. Prominent bony structures were noted in the peri-articular region of left elbow joint.

MRI left shoulder confirmed resorption and lateral subluxation of proximal left humerus with destruction of left glenoid cavity (Figure 2a). Marked T2/STIR hyperintense fluid collection was noted in and around left glenohumeral joint with internal T2 hypointense debris and gross joint distension (Figure 2b).

MRI Cervical Spine with brain screening (Figures 3a–3c) was performed to exclude neurological causes of left upper limb monoparetic oligoarthropathy. MRI confirmed descending transforaminal tonsillar herniation of 9.6 mm compatible with Chiari 1 malformation (Figure 3a). There was a long segment cervicothoracic syrinx asymmetrically involving left half of cord (Figures 3b, 3c).

Background

Neuropathic arthropathy was initially described in 1831 by Mitchell. However, Charcot described this entity in detail in 1868 and demonstrated its causal relationship with tabes dorsalis, thereby establishing a firm association between arthropathy and neurological entities [1]. Common causes of neuropathic arthropathy include diabetic neuropathy, steroid use, syringomyelia, leprosy, spina bifida, and syphilis.

Association between Chiari 1 malformation with subsequent cervical cord syrinx formation and unilateral upper limb neuroarthropathic changes is extremely rare and sparingly described in a few case reports [2–4]. Varying combinations of sensorimotor and autonomic neural dysfunction with superimposed trivial trauma leading to increased local vascularity and progressive osteoclastic activity with resultant pathological joint destruction is the most accepted pathophysiology [1].

Clinical Perspective

Recent onset shoulder joint pain, swelling, and restricted joint mobility merits clinical and radiological investigation to exclude septic arthritis and traumatic injury/dislocation. Co-existing long-standing painless deformity and swelling of left elbow complemented with left upper limb monoparesis and typical radiographic findings prompted further work-up for neuropathic arthropathy secondary to neurological causes.

Imaging Perspective

Plain radiographs of involved joints often reveal varying combinations of 6 “D”s that characterise neuropathic arthropathy, namely joint Distension, increased bone Density, subchondral bony Destruction, intra-peri-articular Debris, progressive joint Deformity and joint Dislocation secondary to lax ligaments. Further, radiographic features may enable sub-classification of neuropathic arthropathy into hypertrophic (fragmentation, debris, osteophytes), atrophic (bone resorption) or mixed forms. Septic arthropathy is a close differential and should be excluded based on clinical and laboratory evaluation.

Radiography findings of neuropathic joints should prompt further historical, clinical, and radiological work-up to evaluate for neurological causes. In this case, typical plain radiography and MRI findings of neuropathic joints involving left shoulder as well as elbow joint indicated further evaluation with MRI Brain and cervical spine. MRI confirmed transforaminal descending tonsillar herniation of 9.6 mm below foramen magnum compatible with Chiari 1 malformation. Also noted was a long-segment cervicothoracic cord, asymmetric syringomyelia causing mass effect on left half of cord. Syrinx is known to interrupt decussating lateral spinothalamic tracts mediating pain and temperature-carrying fibres, thereby explaining left upper limb neuropathic involvement.

Management & Outcome

The current case demonstrates left upper limb neuropathic oligoarthropathy secondary to Chiari 1 malformation. Surgical options are limited due to long-standing disease condition and advanced age. The patient was managed conservatively with protective immobilisation and functional bracing of left shoulder and elbow joints to diminish joint movement related stresses.

Teaching points

Typical radiographic findings of neuropathic arthropathy involving one or more joints restricted to a particular limb(s) should prompt imaging evaluation to exclude central neurological causes.

Written informed patient consent for publication has been obtained.