Investigating the hoarse voice
BMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a1726 (Published 08 October 2008) Cite this as: BMJ 2008;337:a1726
- Pieter M Pretorius, consultant neuroradiologist1,
- Chris A Milford, consultant ear, nose, and throat surgeon2
- 1Department of Neuroradiology, John Radcliffe Hospital, Oxford Radcliffe NHS Trust, Oxford OX3 9DU
- 2Department of ENT Surgery, John Radcliffe Hospital
- Correspondence to: P M Pretorius pieter.pretorius{at}orh.nhs.uk
- Accepted 6 May 2008
Learning points
Any patient with unexplained hoarseness persisting for more than 3 weeks should be referred to an ear, nose, and throat surgeon for investigation
Clinical examination including laryngoscopy is required to identify the small minority of patients with hoarseness who require imaging
Depending on the findings at laryngoscopy, imaging is aimed at (a) characterising and staging laryngeal or pharyngeal tumours or (b) identifying a cause for vocal cord paralysis
Computed tomography or magnetic resonance can be used for either indication, but MRI is preferable if pathology is expected in the brain stem, skull base, or suprahyoid neck whereas CT is better for imaging pathology in the infrahyoid neck and mediastinum
In an adult smoker with a recurrent laryngeal nerve palsy a chest radiograph can be used to decide on the most appropriate form of CT scan to be performed
The patient
A 74 year old man presented with a hoarse voice and difficulty swallowing that had developed over a few months. He also gave a long history of left sided hearing loss. Examination revealed a left vocal cord palsy and a mild left hypoglossal nerve palsy. A vascular mass was noted behind the left tympanic membrane.
What are the next investigations?
Hoarseness is usually caused by excessive voice use, laryngitis, or other self limiting conditions. Referral to an ear, nose, and throat surgeon and imaging investigations are not indicated in patients with a history of hoarseness shorter than three weeks unless it is associated with other symptoms and signs of serious underlying pathology such as unexplained shortness of breath, stridor, dysphagia, haemoptysis, a neck lump, or lower cranial nerve palsies as in this case.1
Clinical examination should include indirect laryngoscopy (with a mirror) or flexible nasolaryngoscopy. This will usually identify the underlying cause of the hoarseness, which may be one of the following—neuromuscular (including vocal cord) paralysis, structural or neoplastic lesions, muscle tension imbalance or functional dysphonia, and inflammatory or infectious conditions. In an observational study of 393 patients presenting with hoarseness after the age of 65, Lundy et al found the cause of hoarseness to be a laryngeal or hypopharyngeal tumour in 16% of cases, vocal cord paralysis in 29%, and muscle tension imbalance or functional dysphonia in 49%.2
Two findings at laryngoscopy should prompt a referral for imaging—(a) vocal cord paralysis or (b) a mass lesion of the vocal cord or other part of the larynx that is suggestive of malignancy or causing significant airway obstruction.
Vocal cord paralysis
This implies loss or reduction of motor innervation by the vagus nerve. It is a sign of underlying disease and not a diagnosis in itself. In a review of seven published studies including a total of 1308 patients with vocal cord palsy, Macgregor et al found that surgical trauma was implicated in 22% of cases, malignancies (predominantly lung and thyroid carcinoma) accounted for a further 22%, inflammatory or infectious causes for 36%, neurological disorders for 4%, and the remaining 16% were idiopathic.3
Imaging is aimed at excluding a mass lesion along the course of the vagal nerve, including its recurrent laryngeal branch. However, imaging is not usually required if the onset of vocal cord paralysis coincides with surgery to the appropriate side of the neck or to the mediastinum in left sided vocal cord paralysis since surgical damage to the nerve can not be detected with current imaging techniques.
No prospective studies have yet estimated the clinical impact of testing on diagnosis or patient outcome, and hence there is no consensus on the choice of investigation.3 4 A retrospective study suggests thorough radiological investigation helps improve the rate of diagnosis by reducing the number of “idiopathic” cases and guides appropriate treatment.5
A mass lesion of the vocal cord or other part of the larynx
Imaging is aimed at characterising and staging the lesion. The most appropriate imaging investigation depends on the clinical scenario including the patient’s age, but computed tomography (CT) and magnetic resonance imaging (MRI) are both suitable for local and nodal staging of laryngeal and pharyngeal malignancies. Because of the lack of research evidence and official guidelines on the suitability of different imaging modalities, our recommendations below are largely based on expert opinion and usual practice. Figure 1⇓ shows our practice for investigating adults with hoarseness.
Fig 1 Investigative pathway for adults with hoarseness
Chest radiography
Non-traumatic and non-iatrogenic vagal nerve palsy in adults is commonly caused by tumours of the lung infiltrating the upper mediastinum on the left (where the recurrent laryngeal branch of the vagal nerve courses around the aortic arch) or, less often, the superior chest wall on the right (where the nerve courses around the subclavian artery). A chest radiograph therefore remains a useful first investigation in an adult smoker with spontaneous unilateral recurrent laryngeal nerve palsy, particularly if it is left sided. A normal radiograph in such patients should be followed by a CT scan from the skull base to below the aortic arch to exclude a more proximal vagal nerve lesion or a small apical or para-mediastinal lung lesion not visible on the radiograph.
In patients with laryngeal or pharyngeal malignancies, imaging is indicated to detect lung metastases or synchronous primary lung cancers. Chest radiography is still commonly used for this, although CT has a higher sensitivity.
Computed tomography
A CT scan from the skull base to below the aortic arch is the investigation of choice in adults with vocal cord paralysis unless there are signs of skull base or brain stem pathology. In many centres, CT is also the investigation of choice for patients with suspected laryngeal carcinoma. For staging head and neck malignancies, the scan should cover the anatomy from the skull base to at least the level of the left innominate vein to ensure that all the relevant lymph node groups can be evaluated.
Modern multidetector helical CT scanners allow the acquisition of high resolution images from the skull base to below the aortic arch in seconds. Such an acquisition covers the entire course of the relevant portion of the vagus nerves as well as the larynx and cervical lymph node groups—that is, the anatomy relevant to the local and nodal staging of laryngeal carcinoma. Given the rapid acquisition times of modern CT scanners, movement of the larynx due to swallowing is not usually problematic.
The use of intravenous contrast material helps in the characterisation of mass lesions and makes it easier to distinguish normal vascular structures from pathology. A further advantage of CT is that, if a suspected malignant cause for recurrent laryngeal nerve palsy is identified, imaging of the chest and liver for staging purposes can be added to the examination. CT also allows the recognition of vascular causes of recurrent laryngeal nerve palsy such as carotid artery dissection, aortic aneurysm or dissection, and right subclavian artery aneurysm.
A CT scan of the neck delivers a substantial dose of ionising radiation, particularly to the radiosensitive tissues of the thyroid. Mazonakis et al used anthropomorphic phantoms and mathematical modelling to calculate that CT scans of the neck in children resulted in absorbed radiation doses to the thyroid of between 15.2 and 52.0 mGy.6 This would be expected to increase the incidence of thyroid malignancy to 390 per million patients. CT of the neck is therefore best avoided in children if MRI is available.
Magnetic resonance imaging
MRI is the investigation of choice in patients with vocal cord palsy where the cause is likely to be in the skull base or brain stem. MRI is also preferred to CT when laryngoscopy has shown a hypopharyngeal mass.
The development of surface coils and parallel imaging techniques have significantly improved the quality of MRI scans of the larynx, but movement due to swallowing remains a problem because of the long acquisition time of MRI pulse sequences. This is more troublesome in the infrahyoid portion of the neck.
Detecting invasion of the laryngeal cartilage is an important aspect of the local staging of laryngeal neoplasms with prognostic and therapeutic implications.7 A prospective study involving 53 patients found that MRI had a higher sensitivity than CT in this regard (89% v 66%), but its specificity was lower (84% v 94%).8 However, this and other comparative studies between CT and MRI predate multidetector helical CT technology, and currently the decision on whether to use CT or MRI in patients with suspected laryngeal cancer rests on local availability and expertise.
MRI offers considerable advantages over CT in imaging the brain stem, the suprahyoid neck, and skull base. It allows exquisite depiction of the relation of a skull base mass with neural structures, including cranial nerves, and with blood vessels and other soft tissue structures below the skull base. There is a common misperception that MRI cannot show bone involvement. Although cortical bone erosion is more easily appreciated on CT, MRI is substantially more sensitive in showing the presence and extent of bone marrow infiltration in the skull base by malignant tumours such as nasopharyngeal carcinoma. In a prospective study of 67 patients with nasopharyngeal carcinoma, MRI revealed skull base invasion in 40 patients compared with only 27 for CT.9
In children, MRI is preferable to CT in order to avoid ionising radiation. Children’s small body size allows extensive coverage of the mediastinum as well as the neck, skull base, and brain stem. Congenital and neoplastic lesions of the mediastinum can therefore be excluded in most cases without resorting to imaging based on ionising radiation.
In a patient presenting with lower cranial nerve palsies in addition to a vagal palsy, the causative lesion is likely to be in the skull base (in or near the jugular foramen, the common exit foramen for the IXth, Xth, and XIth cranial nerves) or the brain stem. MRI with gadolinium enhanced images is the investigation of choice for showing and characterising a lesion in these locations. Bilateral vagal nerve palsies are usually caused by thyroid surgery, but if they develop spontaneously an MRI scan of the brain is indicated to exclude brain stem pathology.
For the small number of patients with an absolute contraindication to MRI—such as those with a cardiac pacemaker, cochlear implant, or incompatible heart valve prosthesis or aneurysm clip—CT is an adequate alternative.
Outcome of this case
In this patient, hoarseness, ipsilateral XIIth nerve palsy, conductive hearing loss, and a vascular mass behind the left tympanic membrane pointed towards a mass lesion of the skull base with involvement of the left jugular foramen, the hypoglossal canal, and the middle ear. An MRI scan of the skull base was therefore considered the most appropriate investigation, and it showed a large soft tissue mass centred on the left jugular foramen and destroying much of the left temporal bone (fig 2⇓). The clinical and imaging features were in keeping with a jugular glomus tumour—a form of paraganglioma. Cardiac comorbidity precluded surgical resection, and the patient was treated with external beam radiotherapy.
Fig 2 An axial, unenhanced, T1-weighted image of the skull base (left) shows a large soft tissue mass (red arrowheads) within the left temporal bone and left side of the clivus. Flow voids (yellow arrowheads) within the tumour confirm the vascular nature of the lesion. Note the normal location and appearance of the right jugular foramen (white arrow) and hypoglossal canal (white arrowhead). An axial, gadolinium enhanced, T1-weighted image at the same level (right) shows avid contrast enhancement
Notes
Cite this as: BMJ 2008;337:a1726
Footnotes
This series provides an update on the best use of different imaging methods for common or important clinical presentations. The series advisers are Fergus Gleeson, consultant radiologist, Churchill Hospital, Oxford, and Kamini Patel, consultant radiologist, Homerton University Hospital, London.
Contributors: CAM selected the patient, PMP and CAM did the literature search, and PMP wrote the paper. CAM reviewed and edited the paper and reanalysed the literature. PMP is guarantor for the paper.
Competing interests: None declared.
Patient consent obtained.