Magnetic resonance imaging characteristics of peripheral nerve sheath tumors of the canine brachial plexus in 18 dogs

Forelimb lameness caused by malignant peripheral nerve sheath tumors of the median nerve in a dog: a case report

An 8-year-old Portuguese Water Dog presented with a 5-month history of left forelimb lameness. There was palmar pain. Ultrasonography revealed enlargement of the left median nerve. Subsequent MRI also showed enlargement of the median nerve in the distal palmar to the mid-forearm region. Rapid intraoperative diagnosis suggested malignant peripheral nerve sheath tumors (MPNST) and a neurotomy was performed. The lameness had almost disappeared in 1 month after surgery. Recurrence occurred 26 months postoperatively and the forelimb was amputated. At 950 days after the neurotomy, radiography revealed lung metastasis, and the dog died 988 days after the neurotomy. Neurotomy for MPNST should be performed with caution until more information is available regarding methods for early detection, margin determination, and indication determination for neurotomy.

Clinical Findings and Outcome in 30 Dogs with Presumptive or Confirmed Nerve Sheath Tumors

Nerve sheath tumors (NSTs) are well-recognized primary nervous system tumors, but there is relatively limited information in dogs including comparison of NSTs in different anatomical locations. This retrospective study describes the clinical features and outcomes in a group of dogs with NSTs affecting the cranial nerves or spinal nerves. Thirty dogs were included, 25 with a presumptive diagnosis and five confirmed by histopathologic analysis. Seven dogs also had cytology of tumor samples, which were supportive of the NST diagnosis in four. Eight dogs had cranial nerve-associated NSTs, with six involving the trigeminal nerve. Twenty-two dogs had spinal nerve-associated NSTs including 13 invading the spinal canal and nine peripheral to the spinal canal, with the majority affecting nerves or nerve roots of the brachial plexus. The prognosis was poor, with dogs being euthanized eventually because of disease progression. Among dogs alive 1 week after diagnosis, the median survival time was 4 months but ranged from 2 weeks to >2 years. While there was a broad overlap between NST locations, survival was generally longer for dogs without spinal canal or intracranial involvement. The results expand available information on NSTs in dogs but should be interpreted with caution given the small number of dogs with a definitive diagnosis. Further investigation is warranted to determine how tumor location, invasiveness, and treatments pursued impact outcome.

Relationship between magnetic resonance imaging findings and histological grade in spinal peripheral nerve sheath tumors in dogs

BACKGROUND

Peripheral nerve sheath tumors (PNSTs) are a group of neoplasms originating from Schwann cells or pluripotent cell of the neural crest. Therapeutic options and prognosis are influenced by their degree of malignancy and location.

HYPOTHESIS/OBJECTIVES

Identify magnetic resonance imaging (MRI) features predictive of PNST histologic grade.

ANIMALS

Forty-four dogs with histopathological diagnosis of spinal PNSTs and previous MRI investigation.

METHODS

A multicenter retrospective study including cases with (a) histopathologic diagnosis of PNST and (b) MRI studies available for review. Histologic slides were reviewed and graded by a board-certified pathologist according to a modified French system (FNCLCC) for grading soft tissue sarcomas. The MRI studies were reviewed by 2 board-certified radiologists blinded to the grade of the tumor and the final decision on the imaging characteristics was reached by consensus. Relationships between tumor grade and histological and MRI findings were assessed using statistical analysis.

RESULTS

Forty-four cases met inclusion criteria; 16 patients were PNSTs Grade 1 (low-grade), 19 were PNSTs Grade 2 (medium-grade), and 9 were PNSTs Grade 3 (high-grade). Large volume (P = .03) and severe peripheral contrast enhancement (P = .04) were significantly associated with high tumor grade. Degree of muscle atrophy, heterogeneous signal and tumor growth into the vertebral canal were not associated with grade.

CONCLUSIONS AND CLINICAL IMPORTANCE

Grade of malignancy was difficult to identify based on diagnostic imaging alone. However, some MRI features were predictive of high-grade PNSTs including tumor size and peripheral contrast enhancement.

Case Report: A Novel Lateral Approach to the C7, C8, and T1 Intervertebral Foramina for Resection of Malignant Peripheral Nerve Sheath Neoplasia, Followed by Adjunctive Radiotherapy, in Three Dogs

This case report describes the diagnosis, management and outcome of three dogs with peripheral nerve sheath tumors (PNSTs) involving the brachial plexus, C7 (case 1), C8 (case 2), and C8 and T1 (case 3) spinal nerves and nerve roots with intrathoracic invasion. Surgical resection required thoracic limb amputation and removal of the first rib, facilitating a novel lateral approach to the spinal nerves and foramina in all cases. This was followed by hemilaminectomy and rhizotomy in cases 1 and 2. Adjunctive radiotherapy was then performed in all dogs. All three dogs regained a good quality of life in the short-term following surgery. Two were euthanased after 3 and 10 months, following detection of a pulmonary mass in one case and multiple thoracic and abdominal masses in the other. The third dog was alive and well at the time of writing (7 months post-surgery). This surgical approach facilitated good access and allowed gross neoplastic tissue to be resected. The ease of surgical access was dependent, to a degree, on the size of the patient. This surgical approach can be considered in cases of PNSTs involving the caudal cervical or cranial thoracic spinal nerves and nerve roots. Adjunctive radiotherapy should be considered as part of a multi-modal approach to these challenging tumors due to the difficulty of achieving clean margins, particularly proximally, even with optimal surgical access.

Neurologic Causes of Thoracic Limb Lameness

Although lameness of the thoracic limb typically is due to orthopedic disease, there are several important neurologic conditions that result in lameness. Neurologic diseases cause lameness due to disease of the nerves, nerve roots, spinal cord, or muscles. Common differentials include lateralized intervertebral disc extrusions, caudal cervical spondylomyelopathy (wobbler disease), brachial plexus avulsion, neuritis, and peripheral nerve sheath tumors. Many of these diseases compress or destroy the nerve roots of the cervical intumescence, resulting in non-weight-bearing lameness, or root signature. Advanced diagnostics, such as magnetic resonance imaging, are necessary in these cases to determine the underlying cause.

Imaging and histopathologic features of reversible nerve root and peripheral nerve edema secondary to disc herniation in a cat

Nerve root enlargement with increased contrast uptake has been reported in dogs and humans secondary to nerve root compression. In cats, nerve root enlargement and contrast uptake only have been reported in association with inflammatory and neoplastic diseases, but not as a sequela to nerve root compression. An 8‐year‐old oriental short hair cat was presented with acute neurologic deficits consistent with left‐sided sciatic nerve deficit and possible L6‐S1 myelopathy. Magnetic resonance imaging (MRI) was performed and identified compression of the cauda equina and L7 nerve root associated with intervertebral disc herniation (IVDH) at L6‐L7 as well as widespread sciatic nerve enlargement with moderate rim enhancement. A hemilaminectomy was performed to evacuate herniated disc material. The nerve root was biopsied and submitted for histological evaluation. Interstitial nerve edema was diagnosed. Follow‐up MRI 3 months postoperatively showed complete remission of the changes. Nerve root thickening together with contrast enhancement may represent nerve edema in cats secondary to IVDH.

Paraneoplastic ganglioradiculoneuritis in a cat with a plasma cell tumour

Case summary

An 8-year-old neutered female domestic longhair cat was presented for investigation of a 48 h history of lethargy and pelvic limb ataxia. MRI of the spinal cord and vertebral column (C1 to sacrum) and brain was unremarkable. Lumbar cerebrospinal fluid analysis revealed pleocytosis and increased protein concentration. Thoracic radiographs and abdominal ultrasound were unremarkable. Anti-inflammatory doses of prednisolone were administered. Clinical deterioration occurred over the following 2 days, with the development of lower motor neuron deficits in both thoracic limbs. On repetition of the MRI, bilateral enlargement, T2-weighted hyperintensity, and marked contrast enhancement of the C7, C8 and T1 nerve roots, spinal nerves and brachial plexuses were observed. Infectious disease testing was negative. An immune-mediated inflammatory process was suspected and immunosuppressive doses of prednisolone were commenced. The clinical signs improved transiently, but marked deterioration occurred after 2 weeks. The patient was euthanased and a post-mortem examination was performed. A lymphocytic inflammatory infiltrate was detected in the C7, C8 and T1 nerve roots and dorsal root ganglia, and neoplastic plasma cells were identified in multiple organs. A diagnosis of non-cutaneous extramedullary plasmacytoma with multiorgan involvement and paraneoplastic ganglioradiculoneuritis was reached.

Relevance and novel information

Paraneoplastic ganglioradiculoneuritis in association with a plasma cell neoplasia has not been previously reported in the cat and should be considered as a differential diagnosis for cats with clinical or imaging evidence of an inflammatory process affecting the nerve roots, spinal nerves or brachial plexuses.

Features of a rare peripheral primitive neuroectodermal tumour arising from the thoracic spine in a juvenile canine patient

Peripheral primitive neuroectodermal tumours are rare tumours in juveniles. The current patient was a paraplegic 8‐month‐old Scottish deerhound with a suspected pulmonary mass. Radiographically, there was a large extrapleural mass within the mid‐left hemithorax. On MRI, the mass was mainly hyperintense on T2‐weighted images, isointense on T1‐weighted images and was heterogeneously strongly contrast enhancing with a multilobulated appearance, spinal cord compression, paraspinal musculature invasion and intrathoracic extension. Those changes were confirmed on post‐mortem, and the mass diagnosed based on immunohistochemistry.

Advanced Imaging of the Forelimb: Use of Musculoskeletal Ultrasound and MRI of the Shoulder and Brachial Plexus

Advanced imaging (ultrasound, computed tomography, MRI) is a key component in defining and localizing the underlying cause of forelimb lameness. Given the propensity of soft tissue injury/disease of the shoulder and brachial plexus, ultrasound and MRI are of particular utility in defining tendinous, muscular, and nerve lesions. An advanced knowledge of shoulder and brachial plexus anatomy is necessary for both image acquisition and interpretation. To determine clinical significance, interpretation of both normal anatomy and suspected pathology must be correlated with clinical signs and orthopedic examination findings.

Cervical hyperaesthesia in dogs: an epidemiological retrospective study of 185 cases

OBJECTIVES

To describe the prevalence, clinical findings and predictors of disease in dogs with cervical hyperaesthesia.

MATERIALS AND METHODS

Medical records of dogs referred for neurological investigation of cervical hyperaesthesia between 2009 and 2013 were retrospectively reviewed. Dogs were assigned to one of the following groups according to the final diagnosis: Non-Neurologic, Brain, Cervical Spine, Multifocal, and Chiari-like Malformation/Syringomyelia. Demographic data, clinical and neurological signs and laboratory findings were compared between groups using univariate analysis; predictors of disease location were assessed by multivariate analysis.

RESULTS

Final diagnostic allocations of the 185 records included in the study were as follows: 2.7% Non-Neurologic, 2.2% Brain, 63.2% Cervical Spine, 22.2% Multifocal and 9.7% Chiari Malformation/Syringomyelia. Intervertebral disc extrusion and steroid-responsive meningitis arteritis were the most common diseases. Compared to Multifocal dogs, those allocated a Cervical Spine diagnosis were older, heavier, more frequently ataxic and lame on a thoracic limb; furthermore, they were less frequently depressed or hyperthermic at presentation. Leucocytosis, neutrophilia and monocytosis were more frequent in dogs allocated a Multifocal diagnosis. Dogs with cervical hyperaesthesia older than 36 months and non-hyperthermic at presentation were more likely to have a lesion of the cervical region rather than a multi-focal disease.

CLINICAL SIGNIFICANCE

Although non-specific, these results may be useful to guide clinicians in management of dogs presenting with cervical hyperaesthesia. Animal age and body temperature may support the suspicion of either focal or multi-focal cervical spinal disease.

Neurofibroma of the ulnar nerve in the carpal canal in a dog: treatment by marginal neurectomy

Peripheral nerve sheath tumours arising in the plexus or peripheral nerves can be treated by limb amputation. There are few reports of these tumours affecting peripheral nerves in the distal regions of the limbs. Here we describe a case of neurofibroma affecting the palmar branch of the ulnar nerve in an Irish setter. Surgical treatment in the region of the carpus by ulnar neurectomy resulted in resolution of chronic thoracic limb lameness. At 11 months following the surgery, clinical examination and MRI did not detect any evidence of recurrence. Neurectomy may be a feasible option for management of selected cases of distally located peripheral nerve sheath tumours.

High dose hypofractionated frameless volumetric modulated arc radiotherapy is a feasible method for treating canine trigeminal nerve sheath tumors

The aim of this prospective pilot study was to evaluate the feasibility and effectiveness of curative intent high dose hypofractionated frameless volumetric modulated arc radiotherapy for treatment of canine trigeminal peripheral nerve sheath tumors. Client-owned dogs with a presumptive imaging-based diagnosis of trigeminal peripheral nerve sheath tumor were recruited for the study during the period of February 2010 to December 2013. Seven dogs were enrolled and treated with high dose hypofractionated volumetric modulated arc radiotherapy delivered by a 6 MV linear accelerator equipped with a micro-multileaf beam collimator. The plans were computed using a Monte Carlo algorithm with a prescription dose of 37 Gy delivered in five fractions on alternate days. Overall survival was estimated using a Kaplan-Meier curve analysis. Magnetic resonance imaging (MRI) follow-up examinations revealed complete response in one dog, partial response in four dogs, and stable disease in two dogs. Median overall survival was 952 days with a 95% confidence interval of 543-1361 days. Volumetric modulated arc radiotherapy was demonstrated to be feasible and effective for trigeminal peripheral nerve sheath tumor treatment in this sample of dogs. The technique required few sedations and spared organs at risk. Even though larger studies are required, these preliminary results supported the use of high dose hypofractionated volumetric modulated arc radiotherapy as an alternative to other treatment modalities.

Intradural extramedullary granular cell tumour in a cat

A 7-year-old domestic shorthair cat was evaluated for progressive paraparesis, inability to jump, a paralysed tail and inability to void the bladder. Neurologic examination was consistent with a L4-S3 localisation. Survey radiographs of the lumbar vertebral column revealed L4-L7 vertebral body remodelling. A pre-contrast T1-weighted hyperintense, diffusely enhancing intradural lesion extending from L4 to S1 vertebral bodies was detected by MRI. Large, mesenchymal, round-to-polygonal cells arranged in nests or sheets were found on histologic examination at post mortem. These cells were characterised by abundant intracytoplasmic PAS-positive, diastase-resistant granules and positive immunoexpression of vimentin, S-100, neuron-specific enolase and desmin. This is the first report of a spinal granular cell tumour in a cat.

Volumetric Modulated Arc (Radio) Therapy in Pets Treatment: The "La Cittadina Fondazione" Experience

Volumetric Modulated Arc Therapy (VMAT) is a modern technique, widely used in human radiotherapy, which allows a high dose to be delivered to tumor volumes and low doses to the surrounding organs at risk (OAR). Veterinary clinics takes advantage of this feature due to the small target volumes and distances between the target and the OAR. Sparing the OAR permits dose escalation, and hypofractionation regimens reduce the number of treatment sessions with a simpler manageability in the veterinary field. Multimodal volumes definition is mandatory for the small volumes involved and a positioning device precisely reproducible with a setup confirmation is needed before each session for avoiding missing the target. Additionally, the elaborate treatment plan must pursue hard constraints and objectives, and its feasibility must be evaluated with a per patient quality control. The aim of this work is to report results with regard to brain meningiomas and gliomas, trigeminal nerve tumors, brachial plexus tumors, adrenal tumors with vascular invasion and rabbit thymomas, in comparison with literature to determine if VMAT is a safe and viable alternative to surgery or chemotherapy alone, or as an adjuvant therapy in pets.

Compartmental resection of peripheral nerve tumours with limb preservation in 16 dogs (1995-2011)

Peripheral nerve tumours (PNTs) affecting the limbs may lead to chronic pain, lameness and/or monoparesis that is refractory to medical treatment. The most common radical therapy for PNTs has been surgical excision with limb amputation. However, compartmental resection with preservation of the limb has been performed by the authors with favourable clinical results and therefore this bi-institutional retrospective study was undertaken to assess limb function, survival and recurrence. Sixteen dogs that had been diagnosed with PNTs between 1995 and 2011 met the inclusion criteria for this study. In the majority of the cases, good to excellent limb function was achieved. The overall median survival time (MST) was 1303days (42.8 months; range, 14 days-4639 days, [0.5-152.4 months]), with two dogs still alive at time of evaluation. Non-infiltrated margins were the best prognostic indicator; dogs with non-infiltrated margins had a MST of 2227days (P<0.001) compared to dogs with infiltrated margins (MST of 487 days). The 1-year calculated survival rate was 68.8% and the 2- and 3-year calculated survival rates were 62.5%. Surgical treatment with tumour removal and limb spare for proximal and distal PNTs can be successful. Compartmental excision can lead to good limb function, producing survival comparable to limb amputation, and should therefore be considered as an alternative to limb amputation in canine PNTs.

3 Tesla magnetic resonance imaging study of the normal canine femoral and sciatic nerves

Understanding the normal course and optimizing visualization of the canine peripheral nerves of the lumbar plexus, in particular the sciatic and the femoral nerves, is essential when interpreting images of patients with suspected peripheral neuropathies such as inflammatory or neoplastic conditions. The purpose of this prospective, anatomic study was to describe the magnetic resonance imaging (MRI) anatomy of the normal canine femoral and sciatic nerves and to define the sequences in which the nerves are best depicted. A preliminary postmortem cadaver study was performed to determine optimal sequences and imaging protocol. In a second step the optimized technique was implemented on 10 healthy Beagle dogs, included in the study. The applied protocol included the following sequences: T1-weighted, T2-weighted, T2-Spectral Attenuated Inversion Recovery, T1-weighted postcontrast and T1-Spectral Presaturated Inversion Recovery postcontrast. All sequences had satisfactory signal-to-noise ratio and contrast resolution in all patients. The sciatic and femoral nerves were seen in all images. They were symmetric and of homogeneous signal intensity, being iso- to mildly hyperintense to muscle on T2-weighted, mildly hyperintense in T2-Spectral Attenuated Inversion Recovery, and iso- to mildly hypointense in T1-weighted images. No evidence of contrast enhancement in T1-weighted and T1-Spectral Presaturated Inversion Recovery postcontrast sequences was observed. The anatomic landmarks helpful to identify the course of the femoral and sciatic nerves are described in detail. This study may be used as an anatomical reference, depicting the normal canine femoral and sciatic nerves at 3 Tesla MRI.

Frameless stereotactic volumetric modulated arc radiotherapy of brachial plexus tumours in dogs: 10 cases

OBJECTIVE

Treatment of canine peripheral nerve sheath tumours (PNSTs) is challenging and prognosis after surgical resection is considered poor. The aim of this study was to evaluate the feasibility and effectiveness of stereotactic radiotherapy (RT) of these tumours.

METHODS

10 dogs with clinical symptoms and MRI findings consistent with PNSTs of the brachial plexus, branches and nerve roots were treated with linear accelerator-based volumetric-modulated arc radiotherapy (VMAT) with a dose of 35 Gy/5 fractions. Clinical and MRI follow-up examinations were planned and radiotoxicity and survival times were investigated.

RESULTS

Tumours involved the plexus and proximal nerves in three dogs, the plexus, proximal nerves and nerve roots in five dogs and the nerve roots and proximal nerves in two dogs. Partial response and partial or complete reductions of neurological deficits were observed in all the treated dogs. Local recurrence was observed in 9/10 of treated dogs. No symptom directly referable to radiotoxicity was observed. Mean overall survival of 371 ± 30 days [95% confidence interval (CI) of (315-427)] and mean progression-free survival of 240 ± 30 days (95% CI of 188-291) from this work are comparable with surgical literature data regarding the plexus and proximal nerve localization, but are superior in comparison with nerve root localization.

CONCLUSION

VMAT can be a safe and viable alternative to surgery in cases of canine brachial plexus PNSTs involving the proximal nerves and nerve roots. Advances in knowledge: To our knowledge, this is the first prospective observational clinical study regarding VMAT stereotactic RT treatment for canine brachial plexus PNSTs and suggests that VMAT may achieve at least similar clinical outcome than surgery in a safer way.

Palliative Epineurotomy for Focal Radial Malignant Peripheral Nerve Sheath Tumor in a Dog

This case report describes the diagnosis of a peripheral nerve sheath tumor of the deep branch of the radial nerve distal to the elbow in a dog. The lesion was identified using computed tomography and ultrasonography and confirmed as sarcoma on histopathological analysis of incisional biopsies. Clinical signs dramatically improved following surgical biopsy before recurring three months later. Repeat epineurotomy of the deep branch of the radial nerve resulted in clinical improvement for a further month before signs once again returned. Epineurotomy as a palliative treatment for peripheral nerve sheath tumors has not been previously described, but may have a place in palliation of clinical signs in specific cases of peripheral nerve sheath tumors in which limb amputation is not an option.

Usefulness of a half-fourier acquisition single-shot turbo spin-echo pulse sequence in identifying arachnoid diverticula in dogs

Single-shot turbo spin-echo sequences are heavily T2-weighted sequences that are exceptionally well suited to evaluate the subarachnoid space. In the T2-weighted fast spin-echo sequences that are used routinely in spinal magnetic resonance (MR) imaging, the subarachnoid space is not well differentiated from the surrounding epidural fat, which could lead to decreased detection of lesions of the subarachnoid space such as arachnoid diverticula. Our purpose was to determine the added value of a single-shot turbo spin-echo sequence in identifying cystic lesions of the subarachnoid space in dogs. MR images of six dogs with a confirmed arachnoid diverticulum and 24 dogs with other spinal disease were included. Six observers were asked to interpret only T2-weighted images initially, and in a second session, T2-weighted and half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences. The MR images were anonymized, and no signalment, history, or clinical information was provided. Without the HASTE sequences, 25% of arachnoid diverticula were identified. Adding the HASTE sequence increased the diagnosis of arachnoid diverticulum to 52.8%. The resulting difference, after adding the HASTE sequence, of 27.8% was statistically significant (P = 0.002). No false-positive diagnoses of arachnoid diverticulum were made with either sequence. Although sensitivity in this study was likely artificially low, the significantly increased detection rate of arachnoid diverticula when using HASTE imaging indicates that this sequence is a valuable addition to MR imaging protocols for the canine spine.

Value of fat suppression in gadolinium-enhanced magnetic resonance neuroimaging

T1-weighted, gadolinium-enhanced magnetic resonance imaging is frequently used to investigate neurologic disease in small animals; however, the abundance of hyperintense adipose tissue adjacent to neural structures, particularly the cranial nerves and spinal cord, can decrease the conspicuity of contrast-enhanced tissues on T1-weighted images. For this reason, chemical fat saturation techniques are used to suppress the signal of adipose tissues, enabling improved depiction of gadolinium-enhanced structures and detection of lesions affecting the nervous system.

Neuropathic pain in dogs and cats: if only they could tell us if they hurt

Neuropathic pain is difficult to diagnose in veterinary patients because they are unable to verbalize their pain. By assuming that neuropathic pain may exist based on the history of events that each patient has experienced, a focused client history and neurologic examination may identify a lesion resulting in persistent or spontaneous pain. Once neuropathic pain is diagnosed, a trial analgesic or acupuncture session(s) should be prescribed with instructions for owners to observe behavior. Dosing of the analgesic can be titrated to the patient's needs while avoiding adverse effects. When a particular analgesic may be ineffectual, an alternate class should be tried. As research into the neurobiologic mechanisms of neuropathic pain continues, specific therapies for its management should eventually appear in the human clinical setting and subsequently be investigated for veterinary clinical use.

Pseudolayering artefact on postcontrast magnetic resonance images of the bladder of 18 dogs and three cats

An artefact was observed on postcontrast magnetic resonance imaging (mri) of the urinary bladder of several small animals; it took the form of a dark layer in the dependent (dorsal) part of the bladder, with a thin hyperintense layer on top of it, and a hypointense signal in the rest of the non-dependent (ventral) part. The mri database was searched for animals with T1-weighted images of the urinary bladder after the injection of gadolinium. Eighteen dogs and three cats were included in the study. The artefact was observed in 16 of the animals on the postcontrast images but not on the T1-weighted and T2-weighted precontrast images. A phantom experiment showed that the signal intensity observed on T1-weighted images decreased rapidly as the concentration of gadolinium increased from 6.25 mmol/l to 25 mmol/l. It is hypothesised that the early excretion of concentrated gadolinium into the bladder causes the pseudolayering artefact observed, which has also been reported in human patients.