Case 1
A 74-year-old man presented with 1-year history of progressive bilateral leg weakness with left side being more affected. He walked with frame in the most recent 3 months. There was no history of trauma or other constitutional symptoms.
Clinical examination revealed moderate weakness (grade 3/5) of the left ankle dorsiflexion, flexion and extension of the left great toe. Otherwise, motor examination of the other muscle groups was normal. Sensation of both lower limbs was intact. The left knee reflex was diminished whereas both side ankle reflexes were absent.
Plain radiographs of the lumbosacral spine showed degenerative changes. Blood parameters showed normal white cell count (WCC), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Magnetic Resonance Imaging (MRI) scan showed a cystic lesion, T1 hypointense and T2 hyperintense with moderate rim enhancement in between dural sac and ligamentum flavum at L3/4 level, compressing and displacing cauda equina (Figure 1A, B).
The patient was treated conservatively with a short course of analgesics and physiotherapy. This regimen failed to alleviate the patient's symptoms. Posterior decompression by L3 laminectomy was performed. Intraoperatively, a cyst was noted in the epidural space spanning the whole of ligamentum flavum in a transverse and cranio-caudal direction at L3/4 level. Two separate ganglion cysts were also found on the dorsal side of both L3/4 facet joints. The dorsal side of the ligamentum flavum cyst extended in a space in the L3/4 interspinous space, whereas the ventral wall was densely adhered to the dura. The cauda equina was decompressed by excising the dorsal cyst wall and drainage of clear fluid inside. The ventral wall could not be separated from the dura and was left in-situ. Further decompression of bilateral lateral canals was performed by undercutting of the facet joints. Both descending L4 nerve roots were decompressed from the shoulders to the entry zone of neuroforamina. Histological examination of the resected specimen demonstrated fibrous connective tissue devoid of lining epithelium.
Postoperatively, the patient showed relief from the spinal claudication symptoms and improvements in ankle dorsiflexion, left great toe flexion and extension power to grade 4/5. He could walk with stick.
Case 2
The second patient was a 56-year-old male optician, who sought orthopaedic consultation because of rapidly progressing bilateral lower limb numbness and weakness for 2 months. Walking tolerance was limited to less than 5 minutes drastically in this period. Left side symptoms were more severe than right side.
Physical examination showed tenderness at lower lumbar spine, weakness of grade 4/5 over left extensor hallucis longus muscle, with decrease in light touch sensation over left L5 dermatome. Straight leg raising test was noted positive at 75 degrees on the left side with tension sign. Lower limb reflexes were intact. All the features were compatible with left sciatica with left L5 radiculopathy.
Radiograph of the lumbosacral spine demonstrated grade I spondylolisthesis at L4/5 level with decreased L4/5 intervertebral disc height. MRI of the same region showed L4/5 disc bulging with severe spinal stenosis (Figure 1C, D).
Posterior decompression by L4/5 laminectomy was performed. A midline cyst arising from the ligamentum flavum with dense epidural adhesion at the midline was noted (Figure 2). The cyst was freed from the dura and excised with some adherent remnants at the midline. Both descending L5 nerve roots were severely compressed in the lateral canals. L4 and L5 pedicle screw fixation, together with Transforaminal Lumbar Interbody Fusion (TLIF) of the L4/5 levels, were also done to correct the spondylolisthesis. On histological examination, there was dense fibrous tissue identified from the cyst wall.
After the operation, the patient could walk with stick without any claudication symptoms. The left L5 radiculopathy was completely resolved.
Case 3
The third patient was an 85-year-old lady with known low back pain on and off for years. She also had history of hypertension, hyperlipidaemia, old cerebrovascular accident. She presented with sudden deterioration in back pain with bilateral lower limb numbness for 1-month. Physical examination showed local tenderness at the lower lumbar region. Lower limb neurology was intact. X-ray of the lumbosacral spine showed degenerative scoliosis. MRI of the lumbosacral spine showed postero-central disc protrusion at L3/4, L4/5 and L5/S1, with lumbar spinal stenosis, L4/5 and L5/S1 facet joint hypertrophy. There was a hyperintense cystic lesion at L3/4 region on T2-weighted image over posterolateral aspect of the dura on the left side, compatible with a ligamentum flavum cyst. However, the patient refused decompression operation due to medical comorbidities. She was provided with conservative management with static progress.