- Loncar, DVM1
Dr Zoran Loncar
- Hadzic, DVM2
M.Dragomirov, DVM2
1,2 Department of Orthopedic Surgery and Neurology, Veterinary Clinic Novak, Belgrade, Serbia
INTRODUCTION
An 8,5 years old miniature schnauzer dog was presented at the clinic with finding of right hind limb monoparesis and grade 1 lameness. CT diagnostic study was done but it was suggested that there was no visible lesions. MRI study shoved a lesion consistent with PNST. The dog was treated surgically and the tumor was excised completely with large margins. The dog recovered completely. The purpose of the article is to suggest that a lesion consisted with PNST distal to the stifle an elbow can be treated with large margins and very good motility of the limb afterwards. This type of pathology can be often missed with orthopedic conditions.
CASE HISTORY
A 10 kg BW, 8,5 years old miniature schnauzer was presented at the clinic with owners complain of lameness on right hind limb for last five months.
At previous vet the dog was submitted to complete orthopedic, radiography and CT study with no diagnosis after the diagnostic workout. The dog was treated with 20 days of NSAID therapy (carprofen 2mg/kg BID 10 days and the dosage was reduced by half for the next 10 days). There was no improvement so the dog was treated with prednisolone for 20 days SID with again very little improvement.
The dog doesn’t have any important data in medical history.
At the presentation in our clinic:
During the walk dog showed grade one lameness.
CT STUDY , Fig 1 and 2
At the clinical examination the dog showed normal proprioception but reduced withdraw reflex on right hind limb. During palpation region of gastrocnemius muscle was markedly painful. The rest of nurology and orthopedic examination was in within normal limits.
CT Study
Figure 1. and 2.
MRI SYUDY Fig 3
MRY STUDY- Fig 4
There is a focal dilation of a vascular structure, presumably a vein, caudal to the medial aspect of the right stifle. The vascular dilation/aneurism has a maximal diameter of 7.7 mm and extends over a distance of approximately 4 cm. Contrast filling of the dilated area is heterogeneous with some areas lacking contrast filling. The affected vessel is an anastomosis/branch between the caudal branches of the saphenous vein and the caudal proximal femoral vein.
MRI study:
Figure 3. T1+contrast: On the right limb at the level of tibial nerve there is a lesion with heterogeneous contrast intake in long contact with blood vessel. The lesion is 3 cm long in diameter.
Figure 4. T1+contrast: Lesion at the level of tibial nerve in close contact with saphenous vein and the caudal proximal femoral vein. Heterogeneous contrast intake.
Figure 5. Surgical field
The surgical approach was made from medial side at the level of proximal part of gastrocnemius muscle. The careful identification of blood supplies and nerve structure was needed. The healthy proximal and distal part of the nerve was identified and the excision with 3 cm margins has been done.
The dog was treated post operatively with antibiotics for 7 days (cephalexin 15mg/kg BID), fentanyl patch for 3 days, carprofen 2 mg/kg BID for 7 days, gabapentin since 3th day 20 days 10mg/kg TID.
Neurological exam has been done after 1,3,6 and 12 months. The only abnormal finding 6 and 12 months post op was longer ground phase during walk and reduced withdraw reflex.
DISCUSSION:
Tibial nerve is in charged for the motor function of caudal aspect of tibia and fibula. Deficit in function shows clinical signs that look similar to orthopedic conditions. Ground phase is longer, calcaneus drops distally more than in contralateral limb. Sometimes we can see plantigrade stance. Orthopedic conditions similar to these in term of signs are pathology of Achill’s tendon and tarsus and metatarsus.
PNST if at the distal part of peripheral nerves can be treated with good outcome. The reasons are fewer functions that lead in less of dysfunction of the limb, and good surgical margins. If PNST is localized at plexus or nerve root, 78% of dogs are going to be euthanized. The prognosis depends on localization and histopathology grading.
CONCLUSION
This article shows how close sometimes can be neurology and orthopedic clinical findings. Even if advanced imaging is available the cruciate information is localization of the lesion during the clinical examination. Further a right interpretation of images is necessary to define the lesion. PNST is an important differential diagnosis in investigation of distal extremities dysfunctions.
